These schools all have minimum GPAs and minimum attendance requirements in order to remain as students.

So the graduation rate, IMO, is a poor proxy for assessing performance. They will have strong graduation rates, by default. It's highly unlikely you will have good grades and attendance and then decide to not graduate.

I mean, let's pretend these schools were horrible [[they're certainly not). They would still have roughly the same graduation rates, since all the "bad kids" wouldn't be counted in the denominator [[they would have all been kicked out beforehand).