That's true, but also the problem. Which university should, then, these best students hang out at? I think we all agree they should be at the one that is the best at teaching them, or which has a style of teaching that works well for them. But we wouldn't know that because most of the ratings can't (or rather won't) discern this. Why is school A the best? It has the best students. Why do they have the best students? Because school A is the best school. So it's not bad for figuring out where the school you belong at is, but a complete non-metric for the school itself - they can't tell how they rate at actual education or if they're a good choice teaching wise (or if all the students would be better off congregating elsewhere - they'd still have each other as well as potentially better teachers).