I’ve read for quite a while that small schools beat larger schools in promoting academic achievement. It’s a plausible argument, but I have never waded deeply into it.
Alex Tabarrok throws a match on the theory, saying it’s all due to misunderstanding a basic fact of Statistics 101.
because small school don’t have a lot of students, scores are much more variable. If for random reasons a few geniuses happen to enroll one year in a small school scores jump up and if a few extra dullards enroll the next year scores fall.
Thus, for purely random reasons we would expect small schools to be among the best performing schools in any given year.