Were kids held back for receiving "needs to improve" in a given subject? If not, then this isn't really the same idea. I totally agree that having "did great"

Were kids held back for receiving "needs to improve" in a given subject? If not, then this isn't really the same idea. I totally agree that having "did great" and "did not so great" as your two types of grade is rather ridiculous if there are no consequences/benefits either way, but basing advancement on mastery rather than age seems like a no-brainer to me.