Oh man, really? That's been my experience in high school, but I was really looking forward to college, where I heard that many professors make homework totally optional and the vast majority of one's grade comes from tests.
You would probably like majoring in math at the University of Minnesota then. The reason to do (self-chosen) homework between the tests is just to be ready for the tests. (Well, really the reason to learn anything should be to learn it, irrespective of grades, but you know what I mean.)
It depends on the college. I would imagine that Stanford would be a bit better quality than my school.
http://www.stanford.edu/class/cs106x/handouts/01-CS106X-Cour...
Your final grade will be computed as follows:
Programs 25 %
Midterm 25 %
Final 50 %
From 51 H, Multivariable Calculus (freshman course)http://www.stanford.edu/class/math51h/51h-info.html
Grading:
Mid-term 1: 20%
Mid-term 2: 20%
Homework: 20%
Final Examination: 40%