Reverse relative age effects in growth and educational attainment in Estonian children born in 1937–62

Background The Relative Age Effect (RAE) occurs when individuals born earlier in a selection period (e.g., school year) have advantages in performance-based fields, particularly sports and education. These older students are often more physically and mentally developed, achieve higher grades and are more likely to pursue higher education. However, RAE can be reversed if parents decide on school enrolment based on their child's readiness. This dataset examines the association between school enrolment age, birth month, anthropometric traits, and educational attainment.

Methods Data from 11 111—26070 Estonian schoolchildren aged 5—19 years, collected by Juhan Aul between 1956—1969, were analysed. Ordinal logistic regression was used to test the effects of morphometric traits and biosocial variables on the cumulative probability of obtaining education beyond the primary level.

Results Only 62% of children were in a grade corresponding to the normative school entry age of seven, indicating widespread early or delayed enrolment and grade repetition. Old-for-grade pupils had more summer births and fewer autumn births, while young-for-grade pupils had more autumn births. All anthropometric traits negatively correlated with relative age-for-grade, with the steepest declines in hip width and sitting height (both sexes), and lung capacity in boys. This relationship also holds for the group of on-time pupils. Birth month had no independent effect on educational attainment. In the whole sample, the odds of obtaining education above the primary level decreased by 28% with each half-year increase in relative age (OR = 0.72, 95% CI = 0.70—0.74). This effect occurred independently of family socioeconomic position, rural vs urban origin, sex, childhood height and cranial volume (each of which had an independent effect on educational attainment). Among the on-time pupils, the effect of relative age on educational attainment was still present but attenuated to 11% (OR = 0.89, 95% CI = 0.82—0.97).