Slackers...so many slackers
Elementary...none to 30 mins
middle school - 5-6 hours not counting weekends
high school - 6-7 hours not counting Fri/Sat - but middle to high school was at a college prep school that promised lots of homework to parents.
college - 3-4 hours a day...it helps not getting busy work or wasting the whole day in class lol
you didn't ask for it, but grad school - only had one semester so far, but 8 seems about average (ranging from 3 to 14), including weekends. This semester's looking up though.