Spending 'hours' on homework usually only happens if they have a long-term project or if there are some unusual circumstances like having makeup work after missing school. When they have to bring regular homework home, it usually doesn't take much time at all.
Although it is not required by the school, my kids like to make sure they have a study hall in their schedule. They use their in-class work time wisely and if they don't finish work in class, they will continue to work on during the study hall. Last year, my 10th grader's study hall was the last period of the day, so that worked out great for him.
Many kids use their study time for other things, like socializing, and that is why they have to bring homework home.
There are a few important personal details at play in my answer. The first is that my teens don't struggle with or need help in any classes. When a child needs assistance it does often take them longer to get their work done.
The second is that the higher level classes where we live tend to focus more heavily on in-class participation and interactive learning. They don't just heap on extra homework to keep kids busy. Your experience will depend on how your son's school operates, but in my kids' experience, getting good grades and taking advanced/AP classes do not necessarily require a ton more homework time.
The rule in our house is that work is to be completed when they get home for the day. This includes Fridays. We don't allow waiting until Sunday afternoon or trying to finish something in the morning before school. There is no staying up late into the night to study when they should be in bed.
If a kid's afterschool activities regularly prevent them from keeping up with their normal daily work, and homework is constantly bleeding into weekends, mornings and late nights, then that something has to change. So far that has not been an issue with my kids' extracurriculars.