Skipping classes as a "gifted" kid always seemed like a very weird concept to me, you're making the child lose a lot of interaction with their peers for dubious reasons. It seems to me like it should only be reserved for the most bulging hyperwrinkled brains, like those kids that finish college by the time they're 16 or whatever that would obviously be extremely understimulated when going the normal pace. Even then you could argue the gigabrain kid would probably benefit greatly from socializing with their peers, I mean where's the rush really? They're young, they can always learn more later.