I think studies found that around 8 hours of work per day are the optimum to maximize performance. That means firms, and also schools, take the best out of you. After having worked those 9 hours, forget about doing an interesting project of your own at home. Your best bet is chilling out in front of the TV.

I want my kid to be able to explore and discover things on his own. Sure, maybe 9 hours of school can be handled - but when will he discover and explore new things?