We did it. The kids were done with school completely by the time their friends got home and were free to play.
The benefits of a custom pace should not be underestimated. Got it? On we go. Don't? Take the time to go over it till they do. No "happy medium" of a class full of students all over the place.
One kid placed into AP Calc in ninth grade. Another in 10th, and went on to a PhD in mechanical engineering with a focus on neuromechanics. They both played sports for clubs and at the high school, and our third climbed for Team USA in international competition.
We basically looked to mainstream them in math at the calc level, to ensure a smooth transition into college classes. And languages, because of course they wanted to study languages -- Chinese, Japanese, Spanish -- in which we had no competency. We were lucky in that the school district here has a policy that if a kid blew through the classes offered at the high school, they'd pay for classes in those areas at the University of Colorado as long as they maintained a C. They could also play high school sports.
One of them was a little immature to sit in a class of college undergraduates, and got into some interests we weren't happy with. We got it sorted, but I want to mention that too. It takes active attention, or they can get their future screwed up. So be serious about it.