High School: Freshman English. Not because it was hard, but my teacher was apparently going through some mental breakdown and we ended up spending half the year reading and writing multiple papers just on Frankenstein. She never returned any work, would misplace papers, spaced out in the middle of lectures, started arguments with students for no reason, showed up with an untreated broken hand, and we literally only read Frankenstein. She commanded no respect, and even though it was a GATE class, kids still messed with her. It was such an uncomfortable experience. She didn't return for the second semester and apparently is a librarian somewhere now.
College: So far, Macroeconomic Theory. So dull, and so many different models to remember.