The heart of school improvement: a multi-site case study of leadership for teacher learning in Vietnam

ABSTRACT This study addressed the research question: How do Vietnamese principals lead the professional learning of teachers? The research was comprised of a multiple-site case study of leadership and teacher learning in four Vietnamese schools. Qualitative data analysis aimed at identifying modal practices adopted by these Vietnamese principals to lead teacher learning in their schools. The research identified four key leadership practices: moral purpose, collaboration, learning support, and motivational strategies. The findings support assertions for a broad set of globally-relevant school leadership practices as well as the need to adapt these to the cultural context of specific schools.

This research has particular relevance in developing societies where the variable quality and limited scope of pre-service teacher education accentuates the importance of on-the-job professional learning among teachers (e.g. Hairon and Dimmock 2012;Hallinger, Piyaman, and Viseshsiri 2017;Lai, Li, and Gong 2016;Li, Hallinger, and Ko 2016;Liu and Hallinger 2017;Liu et al. 2016;Qian, Walker, and Yang 2016;Somprach, Tang, and Popoonsak 2016;Wang 2016). This applies, for example, in Vietnam where the government has recognised that sustainable education reform depends on the ability of principals and teachers to continue learning new skills and attitudes on-the-job (CPV 2001;Hamano 2008;Mai 2007;Mau 1998;Ministry of Education and Training (MOET) 2001;Nguyen 2003). This represents the focus of the research reported in this article. More specifically, our study addressed the question: How do Vietnamese school principals lead the professional learning of teachers?
The research was comprised of a multi-site case study of leadership and teacher learning in four Vietnamese schools. Our analysis aimed at identifying leadership practices used by principals to foster teacher learning. This exploratory study sought to contextualise the findings by linking the identified practices to features of the cultural, political, and institutional contexts of education in Vietnam (Bajunid 1996;Clarke and O'Donoghue 2017;Hallinger 2016;Hallinger and Truong 2014).

Theoretical perspective
In this section of the paper we begin by providing background on the context of education in Vietnam. Then we the conceptual focus of the study.

Context of education in Vietnam
Education in Vietnam Since 1986, Vietnam has carried out the policy of Doi Moi (innovation/reform) which focuses on the social-economic development of Vietnamese society (Duggan 2001;Hac 1998;MOET 2001;Nguyen 2002). Although education was positioned to play a central role in the Doi Moi process (MOET 2001), the education system in Vietnam continues to fall short in terms of the quality of curriculum, facilities, and teaching methods (Duc 2008;Hamano 2008;London 2010;Nguyen 2002). Addressing these perceived shortcomings has been the goal of education reforms enacted since the turn of the millennium (Duc 2008;Duggan 2001;London 2010).
Vietnam employs a bifurcated structure in the provision of education. The Communist Party and the State bureaucracy maintain dual lines of authority over education (Hallinger and Truong 2014). The Ministry of Education and Training (MOET) is responsible for the functional organisation of education (e.g. curriculum, teacher qualifications, education standards, testing). However, authority over the implementation of many of these areas is shared with Communist Party organs at the national, provincial, district and school levels. For example, there is a Communist Party cell in every Vietnamese school which monitors and controls core activities (e.g. teacher and principal selection, curriculum implementation, teacher development) (Hallinger and Truong 2014;Hallinger and Truong 2016;Hallinger, Walker, and Gian 2015).
This division of authority reflects the multiple purposes of education in Vietnam: moral (duc), functional (tai), and political (Doan 2005). Duc refers to virtues or moral qualities of citizens and incorporates values that arise from Confucianism. Duc refers, for example, to the 'right things' expected of people including filial piety, loyalty, respect for 'seniors' as well as to faithfulness to family and society (Dalton et al. 2001;Hoang 2002;Huynh 2002;Nguyen 2002;Truong, Hallinger, and Sanga 2016). Tai refers to knowledge, skills, and competence (Mai 2007). Thus, for example, when a Vietnamese person refers to a 'tai teacher', this suggests that the teacher possesses deep professional knowledge and skilful teaching techniques (Mau 1998;Hamano 2008;Nguyen 2002). Reproduction of the existing political system represents a third purpose of education in Vietnam. Doan (2005) found that a substantial portion of the formal school curriculum is devoted to political and moral education.

Cultural context of Vietnam
The culture of Vietnam reflects influences from indigenous ethnic groups, Chinese Confucianism, Communism, and Western cultures (Dalton et al. 2001;Vien 1984). For example, although social relationships among Vietnamese are strongly hierarchical and collectivist (e.g. Ellis 1995;Jamieson 1993;Vien 1984), Communism has reshaped traditional Confucian values into a uniquely Vietnamese form (Borton 2000;Dalton et al. 2001). Moreover, since Vietnam opened up to the wider world over 30 years ago, Vietnamese culture has been further influenced by Western values of freedom, individualism, and equality (Dalton et al. 2001;Lan 2002).
Nonetheless, respect for hierarchy continues to be a normative feature of social relations in Vietnamese society. Elders expect respect from younger people or those recognised as having lower rank or social status (Dalton et al. 2001;Lan 2002). Respect is expressed by listening attentively and conforming to the advice of 'seniors'. In school settings, 'juniors', whether students, teachers or principals, typically wait for 'seniors' to express their opinion first in order to avoid causing conflict or loss of face (Hallinger and Truong 2014;Truong and Hallinger 2017;Truong, Hallinger, and Sanga 2016).
Vietnamese teachers have long been regarded as among the most important people not only in education but also in society (Hoang 2002;Huynh 2002;Lan 2002). Due to the influence of Confucianism, 'the teacher occupies a central place in the student's life and is revered for the wisdom he provides' (Ozmon and Craver 1999, 117). Teachers are often considered as the pupils' second parents (Huynh 2002). Even the term of address, Con, that students use when speaking to teachers is the same as the term used when speaking with parents (Hoang 2002).
We assert that the role of teachers and principals must be interpreted in light of the context of education in Vietnam (Bajunid 1996;Clarke and O'Donoghue 2017;Hallinger 2016;Hallinger, Walker, and Gian 2015;Huynh 2002;Truong and Hallinger 2017;Truong, Hallinger, and Sanga 2016). This assumption was emphasised in a recent review of research on educational leadership in Vietnam.
We further propose that this particular balance among their [principals'] roles can be traced to values, goals and expectations that pervade the environment of their schools. What it 'means' to be an effective principal [or teacher] in Vietnam must be interpreted within the organisational, political and socio-cultural context of Vietnam. (Hallinger and Truong 2014 , 55) In the current study we believed that it would be impossible to understand how principals lead teacher learning in Vietnam without accounting for the influence of the broader social context (Truong and Hallinger 2017).

Leadership and teacher learning
It is widely accepted that the school principal plays a crucial role in organising and supporting the professional development of teachers (e.g. Cravens 2008;Fullan 2001;Leithwood 1992;Newmann, King, and Youngs 2000;Youngs and King 2002). Indeed development of a 'professional learning community' (Vescio, Ross, and Adams 2008) or a 'learning culture' (Hallinger, Lee, and Ko 2014;Qian, Walker, and Yang 2006;Thoonen et al. 2012) appears to require proactive leadership from the principal (Clement and Vandenberghe 2001;Geijsel et al. 2009;Leithwood 1992;Leithwood and Louis 2011;Sleegers et al. 2014). Thus, scholars who have investigated how 'workplace conditions' influence teachers' engagement in productive professional learning have highlighted the contribution of school leadership (Geijsel et al. 2009;Hallinger, Piyaman, and Viseshsiri 2017;Li, Hallinger, and Ko 2016;Liu and Hallinger 2017;Sleegers et al. 2014;Somprach, Tang, and Popoonsak 2016;Youngs and King 2002). For example, King and Newmann (2001) concluded: Since teachers have the most direct, sustained contact with students, as well as considerable control over what is taught and the climate for learning, it is reasonably assumed that improving teachers' knowledge, skills and dispositions is one of the most critical steps to improving student achievement. (86) Moreover, over the past 30 years, assertions concerning the role of leadership in teacher learning (e.g. Barth 1990;Leithwood 1992;Saphier and King 1985) have moved from normative assumptions to empirically supported conclusions. The efficacy of this conceptual linkage was, for example, highlighted in a meta-analysis of studies of principal leadership effects. Robinson, Lloyd, and Rowe (2008) concluded that the principal's 'participation in and support for teacher professional development' was the single most influential means by which school leadership impacts student learning. This seminal finding encouraged researchers to seek a more refined understanding of how leaders create school-wide conditions that foster the productive learning of teachers (e.g. Geijsel et al. 2009;Hallinger, Piyaman, and Viseshsiri 2017;Li, Hallinger, and Ko 2016;Liu and Hallinger 2017;Liu, Hallinger, and Feng 2016;Sleegers et al. 2014;Somprach, Tang, and Popoonsak 2016;Thoonen et al. 2012).
As noted earlier, the most recent generation of research and practice emphasises that in-service workshops and degree programmes represent an unnecessarily narrow vision of professional learning for teachers (Borko 2004). Scholars have instead proposed that significant teacher learning takes place in the context of job embedded, collaborative, school-based activities (Kwakman 2003;Little 2012;Opfer and Pedder 2011;Timperley 2011;Webster-Wright 2009). This 'social' dimension of teacher learning (Rosenholtz 1989) raises the importance of reshaping modal norms in the schoolhouse from privacy, individualism, and tradition to collegiality, collaboration, and experimentation (Barth 1990;Saphier, King, and D'Auria 2006;Leithwood and Louis 2011;Saphier and King 1985;Thoonen et al. 2012).
These conclusions again reprise the centrality of leadership as a catalyst for professional learning in schools (Robinson, Lloyd, and Rowe 2008). Some leadership practices are 'relational' contributing the development of norms that support teacher learning (Barth 1990;Geijsel et al. 2009;Qian and Walker 2013;Saphier and King 1985;Saphier, King, and D'Auria 2006;Sleegers et al. 2014). Others are 'instrumental', aimed at developing systems and processes that provide tangible support for teacher learning (Hallinger, Lee, and Ko 2014;Leithwood 1992;Li, Hallinger, and Ko 2016;Liu and Hallinger 2017;Qian, Walker, and Yang 2016;Somprach, Tang, and Popoonsak 2016;Thoonen et al. 2012). Research has found that these assertions also apply in East Asian schools where 'hierarchy rules' and teachers are typically more reluctant to step outside of their formally assigned roles (Hallinger, Lee, and Ko 2014;Liu and Hallinger 2017;Liu, Hallinger, and Feng 2016;Qian and Walker 2013;Qian, Walker, and Yang 2016;Somprach, Tang, and Popoonsak 2016;Wang 2016).

Method
This research employed a multi-site case study research design. As Burns (2000) asserted, '[C]ase study is used to gain in-depth understanding replete with meaning for the subject, focusing on process rather than outcome, on discovery rather than confirmation' (460). We used a multi-site research design because evidence from multiple cases is often considered more compelling, robust, and instrumental than a single-site case study (Herriott and Firestone 1983;Yin 1994).

Sample
This research took place in Hong Lam Province Vietnam in the North of Vietnam. We employed purposeful sampling designed to yield 'information-rich cases whose study will illuminate the questions under study' (Patton 1990, 169). Four schools were identified that had been deemed to be effective by the local and provincial education authorities, and which reflected different geographical locations (e.g. urban/rural, and educational levels. Their characteristics were as follows: . School A: Primary school serving 600 students in 15 classes in grades 1-5. Principal Loc, leads 23 staff including his deputy principal. In recent years, the school has been recognised for excellence in academic and moral achievements at the provincial level. Eighteen teachers hold three-year and fouryear bachelor's degrees, and the principal has 15 years of experience as a principal including twelve years at this school. Before being appointed to this post, he had been a teacher for three years and deputy-principal for seven years. . School B: Middle school located in a rural area serving 950 students in grades six to nine. It has been recognised for excellence in academic achievement. There are 32 staff members including the principal and deputy principal. The principal, Ms. Hoa, has 10 years of experience as a principal. Thirty of the teaching staff have three-year or four year training degrees. . School C: An upper-secondary school (grades 10-12) serving 600 gifted pupils from all parts of the province. Approximately 90% of the 12th grade pupils pass the university entrance examination. There are around 50 staff members including Principal Ai, and his deputy-principals. There are 40 teachers of whom seven hold M.A degrees, the rest have four-year training diplomas (bachelors' degrees). . School D: A Teachers Training College serving about 1100 students in five departments. The school is led by the principal, Dr. Dao and his two deputy principals. There are 70 teaching staff. According to the documents, the school has received many rewards from the district, provincial and MOET levels.

Data collection
Data reported in this paper were drawn from semi-structured interviews with the principals, open-ended questionnaires completed by teachers, and direct observation of professional development activities. Semi-structured interviews (see Appendix A; Patton 1990) were conducted with each of the four principals. These aimed at gaining information about the principals' perspectives and leadership practices, as well as and the nature of professional learning activities in their schools. Teachers' perspectives were solicited through an open-ended questionnaire that focused on teachers' needs and motivations as well as professional development practices used in their schools (see Appendix B). A total of 85 of 108 questionnaires distributed at faculty meetings were returned (75% response rate).
In order to gain further details and check on what had been reported in the interviews and questionnaires, we also observed teacher professional development activities in the four schools over a period of two and half months. These observations offered multiple perspectives and enabled the use of triangulation as a means of checking the credibility of different perceptions (Miles and Huberman 1994;Patton 1990).

Data analysis
In this multi-site case study, we employed 'within-case analysis' followed by 'cross-case analysis' (Miles and Huberman 1994;Patton 1990). Within-case analysis involved developing detailed write-ups for each school according to the foci of the research. Analytical procedures first involved coding data based on sources. Next, we organised the data by arranging it into a case record (or database) for each school (Patton 1990).
In the subsequent cross-case analysis we attempted 'to build a general explanation that fit each of the individual cases, even though the cases vary in their details' (Yin 1994, 112). During the process of data synthesis we used open coding, axial coding and the constant comparative method (Glaser and Strauss 1965). We generated categories as we searched for patterns, commonalities and contradictions among four schools (Patton 1990). These categories recognised the importance of taking account of both personal and contextual influences in shaping leadership practices (e.g. see Belchetz and Leithwood 2007;Clarke and O'Donoghue 2017;Hallinger, 2016).

Results
Before reporting results related to leadership and teacher learning, we wish to briefly discuss the nature of teacher learning found in these schools. Data verified the use of both external and school-based professional learning activities. External activities included degree upgrading courses offered by the MOET and universities, seminars, summer workshops, short courses, and district/provincial/national 'good teacher title' competitions. School-based activities included class-observations with feedback, observations of other teachers, weekly professional meetings, mentoring-coaching, and self-study.
Cross-case analysis of professional development activities (not tabled) revealed that the four schools relied quite heavily on 'external development activities'. However, the teachers reported that these external learning activities were often of limited relevance and utility, costly, and time-consuming. In contrast, in-school learning opportunities were generally perceived as more relevant, useful, and related to actual needs of the teachers. Both the limitations of the traditional 'outside-in strategy' and the relevance of school-based learning activities were revealed in comments from one of the teachers.
When we attended the workshop, we did not have much time for demonstration and practice because there were too many people. The specialists just gave presentations, rather than demonstrations. In fact, we don't really learn until we try these new skills in class, observe others using them and get feedback from our colleagues. Those experiences are more valuable because it is more active learning. (Teacher 6,School B) Our data broadly supported the proposition that leadership played a critical role in determining the extent and nature of teacher participation in professional learning activities. Synthesis of the data yielded four leadership practices associated with productive teacher learning: moral purpose, collaboration, learning support, motivational strategies.

Moral purpose
One of the most critical challenges identified by the four principals was helping teachers navigate the change from traditional teacher-centered methods of instruction to student-centred approaches. The principals sought to articulate the basis for this change in terms of 'moral purpose'. More specifically, they worked actively to remind the teachers to keep their students' learning at the forefront of their job and to view their own learning as vital to that of the students.
The ongoing learning of teachers is vital to the health and success of the school. It is like a heart that is beating second by second. If the heart stops beating, life will cease. When the teachers stop learning, so will the students. (Principal Loc, School A) I regard professional development for my teachers as a vital factor to make them develop and improve their knowledge to teach more effectively for the benefit of our students. (Principal Hoa, School B) All four principals conveyed moral purpose through their efforts to make teachers more aware of the impact they could attain through continued development. The principals used a variety of means to articulate this value including speeches at meetings and seminars, individual chats with teachers, public recognition of staff learning and accomplishments, sharing personal learning, and asking teachers to share their successes.
To train 'would-be teachers' to become teachers with both duc and tai is an important task, assigned by the Party, the State, and the people, that demands my great efforts and my teachers' as well. Our teachers must strive to keep developing their own duc and tai even as they seek to develop these same qualities in their students. (Principal Dao, School D) They are aware that I always want them to be innovative, to improve themselves, to discover new things and not to be satisfied with what we have achieved … For me, discovery of new approaches to teaching and learning is both wonderful and necessary. (Principal Loc, School A) The four principals set general regulations for teachers' professional development. The principals considered their teachers' needs and family situations in order to select appropriate strategies. For example, female teachers with young families or teachers in financial difficulty could postpone required certificate upgrade courses. Teachers regarded this individualized consideration for individual conditions as a reflection of the principal's duc.
In all four of the schools, teachers suggested that they viewed the principals as role models. Teachers in School A respected Principal Loc for his knowledge of curriculum, teaching and learning. Teachers in School D respected Principal Dao because of his high qualifications, experience, awards and 'commitment to learning new things' (Teacher 9, School D).
Moral purpose was, therefore, interpreted and articulated by the principals as the teacher's responsibility to society (i.e. Confucian norms), to the Communist Party (political norms), and to education reform (institutional norms). Responses in the teacher questionnaires suggested a general acceptance of this multifaceted rationale for learning and change. Take, for example, comments from several teachers from School D.
We must show that we are capable of change before we can teach students how to adapt to the changing expectations of society. (Teacher 3, School D) During the current educational reform, our own learning and development are critical to success. We have to master changes in both subject knowledge and teaching methods to contribute to the reform. (Teacher 1, School D) If this [teachers' professional development] is not done well the nation's efforts at educational reform cannot succeed. (Teacher 9, School D) My desire to continue learning stems from my commitment, conscience, and responsibilities toward my students. (Teacher 5,School D) In sum, moral purpose was used by the principal to make institutional goals for educational reform meaningful in the minds and hearts of teachers. Their ability to accomplish this was enhanced by cultural norms that legitimated hierarchy in social relations and honoured the role of teachers in Vietnamese society. Similarly within the authority-oriented education system of Vietnam, teachers appeared willing to accept nationally endorsed institutional and political priorities for educational reform as 'legitimate'.

Collaboration
Central in the minds of the principals was the need to foster collaboration in professional learning. Collaboration seemed to be built on a foundation of trust and collective responsibility. Within the Vietnamese culture, community is interpreted as 'collectivist', meaning that there is cultural bias towards thinking of 'we' rather than 'me'. Accordingly, individual teachers were expected to place the good of the group ahead of their individual benefits. That said, Vietnamese people can also be quite competitive. Thus, norms of collaboration for teacher learning required active nurturance from principals, middle-level leaders, and teacher leaders.
As noted, social relations in Vietnamese 'communities' are implicitly structured according to age, seniority and rank. The principals demonstrated an intuitive understanding of the cultural importance of giving face to senior teachers. Recognition of their special role in school and society legitimated their expertise and engaged them in continued learning.
The experienced 'older' teachers are very significant in the life of our school. 'Old' does not refer only to age, but also to their professional knowledge (tai) and personal qualities (duc) that distinguish them as valued teachers. In our school, older experienced teachers help the younger, less experienced ones. This is a good solution for all of the teachers since by helping the younger teachers, the older ones stay engaged and continue to learn as well by sharing their knowledge with others. (Principal Hoa, School B) This social norm was also recognised and valued by the younger teachers. As one young teacher wrote: I have learnt much from more experienced teachers through observing their lessons, especially teaching skills that I am not good enough at … I can learn how to manage the class. I take notes on the techniques and practices used by my colleagues to read again later. (Teacher 6, School A) Collaborative learning was evident in a variety of ongoing activities including school or department-based seminars, mentoring, coaching and weekly professional meetings. These provided teachers with opportunities to discuss professional issues one-on-one, in small groups and in larger forums. Professional learning also emerged through collective problem-solving, such as when colleagues offered help to colleagues in difficult situations.
All four schools held 'weekly professional meetings' as a regular opportunity for teachers to discuss issues related to student learning. These problem-focused meetings were organised by teachers who typically gathered with others either by departments or smaller groups. Principals participated regularly in these meetings rotating among the groups as their time permitted. Most teachers regarded their principal's participation in these meetings as a source of encouragement and believed it demonstrated 'caring' for the challenges they faced.
Principals saw their role as both facilitating the organisation of collaborative activities and ensuring that they remained focused on teaching and learning issues. As Principal Loc observed: 'Professional meetings must be realistic, scientific, and regular. If professional meetings do not meet these requirements, they will not last long and will not be effective because teachers find them boring and unnecessary' (School A).
In these schools, the principal's engagement with teachers on issues of teaching and learning was grounded to varying degrees in expertise in teaching and learning that may or may not typify principals more broadly in Vietnam. At times this extended beyond support for and participation in workshops and professional meetings with their teachers. This was expressed by one of the teachers in School A.
My principal understands the curriculum, the textbooks and teaching techniques rather well. He has good ideas about teaching and learning as shown during professional meetings or observations. Sometimes, he has taught a model lesson for us to observe and discuss. (Teacher 5, School A)

Learning support
Another critical role of leadership involved providing support for teacher learning (Hallinger, Lee, and Ko, 2014;Leithwood 1992;Liu and Hallinger 2017;Newmann, King, and Youngs 2000;Saphier, King, and D'Auria 2006). In these schools, the management board, chaired by the principal, was in charge of this task. However, the principals varied in the extent to which they were personally involved in providing learning support to teachers. For example, Principal Loc was very close to his teachers and showed great enthusiasm, energy, and commitment when participating in seminars or meetings with his teachers. The other three principals tended to delegate this support function more to middle-level leaders. Nonetheless, all four of the principals seemed eager to see the new learning of individual teachers shared with others and applied in classrooms.
I think that the workshops and courses are necessary, especially those relating to textbook replacement and reforms in teaching methods. However, it is more important that our learning from those workshops and courses is applied successfully to our classrooms … Thus, follow-up activities for drawing experiences are valued and encouraged. (Principal Hoa, School B) The principals were quite intentional in helping to arrange for teachers to observe other teachers when implementing new skills or curriculum content. For example, Principal Ai in School C required teachers to observe one lesson per week taught by another teacher. Periodically, all teachers were expected to teach a model lesson and participate in follow-up discussions.
The principals also sought to create opportunities for teachers to share new learning in ongoing meetings. This cycle of learning, discussion and observation was considered crucial to the success of professional learning not only by the principals, but also by the teachers.
In my view, both observers and observed teachers learn from these teaching observations and discussion. When observations are conducted, the teacher being observed is typically more careful than usual in preparing the lesson. After the observation, all participating teachers … contribute their ideas to the discussion by pulling out the good points and pointing out several points that can be done better next time. This is really good for both the observer(s) and the teacher who taught the lesson. (Principal Loc, School A) I learned teaching methods at college and got some practice during posting time. But I know that I still need more experience to learn how to use these [methods] in my classes. Now I am learning by observing colleagues' lessons and getting feedback on my lessons from more experienced colleagues. (Teacher 8, School B).
Comments from two young teachers articulated why it was important for the principals to build trust as a foundation for this kind of professional exchange. I prefer observing other teachers more than being observed. I often feel nervous when seeing other teachers, especially senior teachers or an administrator sitting at the back of the class watching me teach. (Teacher 4, School A) In fact, I don't think anybody really likes to be observed while teaching. But if we can overcome our shyness, most of us are actually thrilled to get feedback from their colleagues and especially to be evaluated on our skills and practices. (Teacher 2, School A) With this in mind, all four principals set up systems whereby teachers were observed by colleagues. In doing so, however, they emphasised norms of 'positive growth'. Principal Loc in School A stressed that observers should 'have a smiling and friendly face' and keep a positive relationship to reduce the observed teacher's nervousness. The observer's role is to 'give constructive feedback, not criticism'. In School C, Principal Ai elaborated that 'A friendly attitude towards one another is required in discussion after the observation … This can help relieve pressure upon the teacher being observed'.

Motivational strategies
The four principals used systems of formal and informal reward and recognition to sustain teacher involvement in professional learning. These included a mix of social, financial, political and psychological incentives. Although both 'public' and 'private' rewards were employed by the principals, the use of public recognition was a notable feature in the Vietnamese school context.
Teachers who contributed to the achievement of school targets in the domains of teacher competency or professional development received small monetary rewards delivered in a public setting. Examples included successful completion of degree upgrading courses, attainment of a 'good teacher' title in a district, provincial or national competition, and a positive assessment on a research study. In the eyes of the principals, both the financial reward and public recognition for the achievement represented strong 'culturally-appropriate' motivators.
For example, Principal Loc in School A asserted: 'A small gift serves as a kind of reward and recognition. Although the reward may be small, it offers great encouragement for that teacher when given in front of her colleagues.' This practice mirrors an indigenous cultural practice in Vietnamese society where the ritual, 'offer of a small gift of food to a person in front of the whole village is considered more precious than a large basket of food given privately to a person in the home' (Principal Loc, School A).
These forms of extrinsic reward for professional learning were standard practice in all four schools. Although these kinds of rewards seemed to appeal to the teachers' sense of competition, it was more often than not channelled into competition on behalf of the school. This reflected the strong collectivist norm in Vietnamese culture and appeared to influence teachers' motivation to engage in professional learning.
Although these extrinsic motivational strategies were the most obvious ones, we also noted intrinsically-oriented strategies, in particular the 'reward of spirit'. This term was repeated in both the principal interviews and teacher questionnaires. The respondents articulated that the behaviour of their students and appreciation and respect of colleagues and parents represented a meaningful reward for Vietnamese teachers. Numerous teachers explicitly asserted that their professional development was important to them because it could them help improve the learning and achievements of their 'dear students'. This motivation reflects the influence of Confucian values which reinforce both the respected role and high level of responsibility held by teachers in Vietnamese society (Huynh 2002;London 2010;Ozmon and Craver 1999).
This finding connects back to the power of 'moral purpose' as a foundation for teachers' professional learning in these schools. Indeed, all four principals indicated that they drew upon this 'intrinsic motivator' by reminding teachers explicitly and often about the honour of becoming a teacher capable of demonstrating both duc and tai in Vietnamese society. This engendered a sense of responsibility and discipline among the teaching staff which the principals asserted complemented the use of extrinsic rewards for engaging in successful professional learning.

Discussion
In this study we examined practices used by four Vietnamese principals to support the professional learning of teachers. Although our perspective on leadership and teacher learning was initially shaped by Western literature, the use of a qualitative research methodology allowed for an exploratory rather than a confirmatory approach to knowledge building. Thus, we inductively identified and described leadership practices within four broad leadership strategies. Our cross-school synthesis paid particular attention to how these practices reflected the context of Vietnamese society. In this concluding section of the paper, we briefly discuss limitations of the study, interpret the findings, and highlight implications for research and practice.

Limitations of the study
Like other case study research, this study involved a limited non-representative sample. Therefore, our findings cannot be generalised to the population of Vietnamese schools and educators (Yin 1994). In addition, it is possible that features of Vietnamese culture could have exaggerated a tendency for informants to provide an overly positive picture of practices in their schools. Vietnamese people behave in accordance with the Vietnamese idiom: 'good things are revealed and bad things should be covered up (tốt khoe xấu che). Although our use of data triangulation, especially observations, sought to address this threat to validity, we acknowledge this as a potential limitation of the study.

Interpretation of the findings
The study identified a wide range of 'external' and school-based professional development practices across the four schools. Our cross-case synthesis identified four broad leadership practices used by the principals to motivate, support and sustain the professional learning of their teachers: moral purpose, collaboration, learning support, and motivational strategies. These leadership practices were, however, adapted to fit the political, cultural, institutional context of Vietnamese schools (see also Truong and Hallinger 2017;Truong, Hallinger, and Sanga 2016). The model of leadership and teacher learning which emerged from the cross-case synthesis is shown in Figure 1.
Each of the four principals regarded moral purpose as an indispensable quality (duc) necessary for the successful fulfilment of their role. As noted earlier, the institutional context of education in Vietnam is strongly hierarchical with policies expressed as 'decrees' handed down from higher levels (Hallinger and Truong 2014;Truong, Hallinger, and Sanga 2016). Thus, a leadership challenge faced by each of the principals was to interpret institutional policies and programmes in terms of moral purposes that would be meaningful to the teachers (Truong and Hallinger 2017;Truong, Hallinger, and Sanga 2016).
The collectivist culture of Vietnamese community emphasises the common good before the rights of individuals. Thus, when the principals articulated 'moral purpose' as a foundation for the continued learning of educators it also revealed their sense of responsibility to the collective good of the school, community, Party and society (Truong and Hallinger 2017). The individual rights of both teachers and students were secondary to the needs of the group (Dalton et al. 2001;Lan 2002;Truong, Hallinger, and Sanga 2016). Moral purpose was also revealed in the responses of teachers for whom their contributions to collective interests formed a paramount value and source of meaning for their work. This interpretation of moral purpose stands in contrast to Western societies where moral purpose is increasingly interpreted in terms of 'social justice' defined as individual rights.
Leadership practices that fostered collaboration reflected a cultural value of maintaining harmony within the community (Dalton et al. 2001;Jamieson 1993;Lan 2002;Truong and Hallinger 2017;Truong, Hallinger, and Sanga 2016). Although this appeared to support the norm of collaboration, Fullan's admonition that '[C]lose relationships are not ends in themselves ' (2001, 67) was also applicable in these settings. Indeed, an ever-present cultural challenge for the principals was to maintain harmonious relations without sacrificing the interests of students (Hallinger and Truong 2014;Truong and Hallinger 2017).
Collaboration in the Vietnamese context was also shaped by norms of hierarchy (Borton 2000). Age, status, experience, and even gender could easily create an 'invisible distance' between the teachers and their principals and also among the teachers. Thus, the 'warp and woof' of collaboration had a different character from descriptions in the Western literature (Barth 1990;Fullan 2001;King and Newmann 2001;Little 2012;Rosenholtz 1989).
Although the internationally-accessible literature on educational leadership and management in Vietnam remains limited, recent reviews of research have suggested that 'instructional leadership' has not been emphasised in the Vietnamese education system (Hallinger and Truong 2014;Hallinger, Walker, and Gian 2015). Our findings related to the provision of 'learning support' for teacher development contrasted with this conclusion. These four principals viewed the improvement of teaching and learning as central to their role and were meaningfully engaged with the development of teaching practices in their schools. The most significant form of learning support was represented by normative practices associated with principal-teacher and teacher-teacher observation and feedback.
There were two notable features of principal leadership in this domain. First, the principals were quite 'intentional' in developing norms of positive feedback and growth among the teachers. This was viewed as essential to the success of teacher observations, whether by administrators or other teachers. Second, the principals developed systems that supported teacher observations of other teachers as a core practice aimed at ensuring that learning was transformed into practice. This reprises Fullan's (2010) assertion of the need for 'positive pressure' as a condition to support the implementation of change in schools.
Motivational strategies employed by the principals can also be interpreted in light of the Vietnamese context. The use of small financial rewards given to individuals in public forums, contrasts, for example, with American schools, where the use of rewards for individual teachers is challenged by cultural norms of equality (Malen 1999). At the same time, however, the principals also drew explicitly upon moral purpose as a motivator for sustaining teacher engagement in professional learning. This was embodied, for example, in their use of the 'reward of spirit' or the honour of fulfilling the role of a teacher with both duc and tai in Vietnamese society. This reflects Fullan's view: '[I]n the long run … effectiveness depends on developing internal commitment in which the ideas and intrinsic motivation of the vast majority of organizational members become activated ' (2001, 46).

Implications of the findings
The leadership practices identified in this study echo themes that have been well documented in Western societies (see Barth 1990;Geijsel et al. 2009;King and Newmann 2001;Newmann, King, and Youngs 2000;Robinson, Lloyd, and Rowe 2008;Saphier, King, and D'Auria 2006). Nonetheless, it was quite clear that the implementation of these strategies in Vietnamese schools had a flavour that reflected the influence of the Vietnamese context. Future research on educational leadership in Vietnam should assess the extent to which the practices of these four principals are represented in the leadership enacted by the larger population of Vietnamese principals.
The practices described in this paper also offer insights that can be employed by principals in Vietnam and in other societies. Indeed, we suggest that the advantage of the contextualised lens adopted in this study offers practitioners the opportunity to consider the contingencies that shape the selection of leadership strategies. This seems to us preferable to a 'menu-driven' approach to describing 'effective leadership' as if it applies in all settings. Thus, the findings support the contention that a broadly similar set of successful leadership practices take on different patterns in different societies (Bajunid 1996;Belchetz and Leithwood 2007;Clarke and O'Donoghue 2017;Hallinger, 2016). This leads to a further recommendation for additional qualitative research that elaborates on and connects leadership and learning practices to the contextual features of different societies (Hairon and Dimmock 2012;Hallinger, Piyaman, and Viseshsiri 2017;Liu and Hallinger 2017;Qian, Walker, and Yang 2016).
Throughout this paper, we have compared our findings in Vietnam to studies of leadership and teacher learning conducted in Western societies. However, it should be noted that in recent years an increasingly rich literature centreing on this topic has begun to emerge in East Asia with studies from Hong Kong (Hallinger, Lee, and Ko 2014;Lai, Li, and Gong 2016;Li, Hallinger, and Ko 2016), mainland China (Liu and Hallinger 2017;Liu, Hallinger, and Feng 2016;Qian, Walker, and Yang 2016;Qian and Walker 2013), Thailand (Hallinger, Piyaman, and Viseshsiri 2017;Somprach, Tang, and Popoonsak 2016), and Singapore (Hairon and Dimmock 2012). Future research should assume the challenge of examining commonalities and differences in these practices within East Asian societies. This will not only offer policymakers and practitioners insights into 'leadership paths that make a difference' for educational quality, but also contribute towards building a more diverse global literature in educational leadership and management (Bajunid 1996;Clarke and O'Donoghue 2017;Hairon and Dimmock 2012;Hallinger 2016).

Disclosure statement
No potential conflict of interest was reported by the authors.