The holdbacks are a boy thing, although the coed schools have some pre-first programs, it’s just a way to get another year of tuition out of a family rather than them having to admit that they held their son back a year or started late. It’s a weak argument.
You are delusional if you think it’s just a boy thing.
If you think girls are being held back and repeating grades in middle school for lacrosse purposes you are the delusional one.