I had some bad classes! Got a couple Bs that should have been As, if I'd really studied. One of my two Cs could have been a B... but I learned a lesson about goofing off. And about how to study.
History was never an issue for me. I just read a lot in high school, then when I got to college everything was watered-down pap. But dates were hard. And trying to keep Louis XIV and Louis XVII straight... no, thanks.
In my case, I've always been good at tests...I could study the night before and do OK...
But nothing sticks! In some ways that's kinda fun...I can reread a book or watch a movie again just a short time afterwards, and it's all new. ;-) But I really wish I didn't have such a lousy memory. No matter how carefully I read something and go over and over it, I forget most of it in a short time.