I do think kids/students can burn out, particular around the teen years. But it's not just 'our' kids. Many of the hot housed kids weather they are PG or not, work so hard particularly as teens that they never have ANY downtime. And they often get pushed into directions in school that aren't particularly their choice.

I've also seen kids burn out in sports.

By the time school is out for the summer, my DS is very burned out and wants nothing to do with any schoolwork. I seen teens who never seem to have ANY time even in the summer to let their hair down. Some of them don't handle this too well.