This is what happened during my high school job.  They hired a lot of 16+ year old high school students, and many of them left for college at around 18 or 19, when they graduated high school. So there was a lot of turnover from people just progressing with their lives.  Advantage being, you still have competent employees for a couple years before they move on.    Management got tired of hiring new people, so started a new policy - 18 or older only.  So now, almost no highschoolers were hired.  Except the ones who didn't do anything after high school, other than sit in their rut.  But are those the type of people you want working for you?    Unsurprisingly, the workforce went from about 70% decent people who work hard, to about 10% decent people who work hard.  Average employee BMI also shot up.    They started this policy shortly after I was hired (at 16) so I got to watch first-hand, as people a year older than me quit to go to college, only to get replaced by complete morons who could barely function.