In my case it was a weekend of messing around with C in grade 10 (I made an ASCII Pac-man program...still runs just fine on Vista
). Technically that was homework, but I think I could have done a much lesser project in-class and still got perfect marks.
I'm absolutely certain I had nowhere near 400 hours of homework (assuming 900 hours of class is about what I had...I really don't remember how many days of school I had in a year -- 150 days @ 6 hours / day seems low to me, actually, but uncharacteristically I don't feel like figuring it out). I normally completed homework at lunches (we had alternating daily schedules, so one set of classes was one day and another set the next), with extremely rare exceptions, so it was no more than ~1/6 of my class time; and most lunches, honestly, I did nothing but read or, rarely, socialise. It could be that I'm just hyper-brilliant, or it could be that my school was just way lighter on homework and more generous with in-class work-time. Or both. Or maybe I'm SUPER-hyper-brilliant and my school was heavier on homework than elsewhere
Edit: with that said, I swear: my high school education was no more and no less bullshit, on average, than my University education (top-tier University, doing Engineering Physics). Some things were bullshit, some teachers were bullshit, and that really didn't change. What changed was the narrowness of my courses (far more math & science, far less social studies), which was neither great nor terrible for me. I grew up in a rural area and went to University in a giant city. Some of the things you call high school subjects make me SO jealous. My options in high school were called: Grade X Math, Grade X Science, Grade X English, Grade X French, Grade X Phys Ed., Grade X Music, Grade X History, Grade X Drama, Grade X Art, Grade X Computers (one-time only this was offered on the exact years I went through school, and apparently in large part because I and one of my friends were that age...small town, that could actually be arranged for one of the kids who actually intended to go out into the world), Grade X Geography, Grade X Shop & Tech, and Apprenticeship (aka slave labour manning the cash register for a local merchant, counts as 4 courses). Choose 8 per year. There was also accounting for two years, and girls-only could do dance for a year, there was one year of Economics and a few extra math, science, and history courses for what you might call "grade 13" in your foolish mortal 12-grade school system.