College is different from high school. In high school I could go to class, not study at all, and do great. Wouldn't work in college, you actually have to do work on your own outside of class.
Oh, and an hour long class in college means that the professor will be teaching for the entire hour. There's no "work time" or stuff like that, and if you don't pay attention, you'll get lost quickly, especially if it's a small class.
And that cookie-cutter advice of "go to class" and "study" may be over-repeated, but that doesn't mean it's not true.