The number of kids repeating grades is high school is relativity low
But many of them are only repeating grade for athletics
Shame on the parents and administion who turn a blind eye to it
I think you are mistaken on this point, if you look nationally across all sports, i think you will find that many kids are held back, it may happen prior Middle School but it does happen. If a graduate is 18 at graduation, chances are, they are held back at some point in their schooling.