I've heard from many of the people on my friends list that they tended to disengage. There were probably a few behaviour-problem smart kids, too. My brother did some of that. His opinion is that he was ignored, he was not taught the study skills he needed because he learned content so quickly that everyone thought he didn't need the study skills, and when he got to university, the lack of work habits combined with burgeoning depression resulted in the eight years he's spent getting a three-year degree. The school system did very poorly by him, and I understand why he's down on teachers in general for that.