Of course, the assumption here is that grades should represent how well a student knows the material, not how hard they worked in the class. I know a number of teachers I had used that philosophy, despite the clamoring of the kids at the top of the class.

Now that I'm not there anymore, I actually agree with them. Classes don't exist simply to teach course material - there is a lot of stuff you learn simply by doing all the work. Consider a lit course. The stated goal of the course might be reading and analysis of the course texts, but you also get better at writing simply because you did the "busywork".

The same holds for quantitative classes. There's only so much you can test in an hour, even if there are tests every week. Longer problem sets cater to a different skill set that tests, and they are both worth learning. A class that lets you skate by on pure test-taking ability misses a large chunk of the education.