I always did well on tests and in any class I didn't totally hate I felt like I gained the knowledge I needed to. However, I never did all the homework. Hated it. Most of it felt like busy work, or just plain unimportant.
Not that I think self-discipline is worthless. It is a very important life skill. But they don't really teach you how to be self-disciplined so much as attempt to force it on to you by making your grade dependent on a ton of extra work. I like the idea of splitting grades into knowledge and self-discipline like the Minnesota school did.