My 6th grader has about two hours of homework a day plus saxophone practice but he's in a magnet program that is writing and project intensive AND he's taking Japanese. There is always an additional writing assignment on the weekend but it's usually a short one. He knew what he was getting into. He also has Hebrew to practice everyday but that's rarely more than 15 minutes.

In general, the teachers seems to be aware of big assignments so it is uncommon for him to have major work or an important test at the same time a major project is due in another class.

The High School kids I know well are in an International Baccalaureate program and have 2.5-3 hours most nights.