Something that's graded is given a rank or a score, like your Calculus test.
The root word grade comes from the Latin gradus which means "step or degree." Graded rankings are arranged by step––one step up from a grade of B is a grade of A, and a slope is graded, rising not by steps but by degree. Note that graded can be used as an adjective, as in "She handed out the graded tests," or as a verb, as in “He graded the slope around the basement.”