This is an honest question from a childless person: how much time does your 3rd grader spend doing math homework per night?

Naively, it seems reasonable to me that there is going to be a fraction of the necessary practice which must be done under the supervision of the teacher, and a fraction which can be done alone. Now, as people move up the academic ladder and, presumably, become better at teaching themselves, the amount of class time decreases and the amount of self-directed time increases.

At the 3rd grade level, where they spent 6-8 hours in class each day, it seems plausible that the correct amount of homework is roughly 30-60 minutes per night. It also seem plausible that the homework teaches a student not only the material, but also how to learn on their own.