No mandatory homework period.
My high school life was:
2 hours of commuting to and from school...which was to get me into a school I actually learned in instead of spending all my time dodging bullies.
8 hours of school, with a one hour lunch break.
2 hours of mandatory homework every single night.
So, we're already at 12 hours. With 8 hours sleep, we're at 20 hours. Call it 90 minutes to eat and I had 2 and a half hours of "free" time.
Oh, except I had to do about 2 hours a day of extracurricular activities.
And most kids have it worse than I did, they might not have the 2 hour commute, but I know of high school kids who have:
1 hour commute.
8 hour school day.
4 hour part time job.
2 hours homework.
2 hours extracurriculars.
Add 8 hours to sleep and you're at 25 hours...when do these kids eat?
And sure, the extracurriculars are probably stuff they want to do.
But the entire system is designed to train kids to be workaholics.
Instead of mandatory homework, kids should receive reading lists of books and blogs, TV shows or movies that represent the subject well, etc. None of which they would be graded on, it would be designed to help them find the subjects they are enthusiastic about for college, future hobbies, etc.