As a highschool student, I can tell you that the problem isn't limited to just the top universities; most of my friends and I get around 6 hours of sleep a night, and it's definitely not enough. Some nights I've gotten as little as 2 or 3 hours, but I disagree that this is the best way to learn material, because I don't remember a) any of the material I was studying or b) anything I may have learned in class the next day.