Hardest class for me was Honors Bio 2. No joke. The first day, the prof raised the book up and said, how many of you studied this in your AP class in high school? Everyone but me and the guy next to me raised their hand. He said "Ok, I'll just assume you know that book's material, then, and we'll move on."
I hadn't taken AP bio. God that class was hard. Got a 4.0 still, though! 👍