My teacher wasn't bad last year, but she had a nasty habit of assigning tons of things without set due dates. She'd say read boatloads of pages in your book and do all of the margin review, big picture, and document questions within maybe a week or two. As someone who can't focus enough to finish most of the projects I start on my own accord, that was torture.
And then we had to study for the AP test towards the end of the second semester along with all that annoying book stuff.
It's never so much been that I can't deal with the concepts, it's more about the specifics that bug me. All those little details that I just sort of have to remember to deal with any given equation just drove me insane with chemistry.
What science did you take last year?