Surprised I'm the first person to say this, but I think it all heavily depends on what your specific strengths and weaknesses are, as well as your interests.
You're going to have a harder time in a subject that you have little interest in. You're going to do better and have an easier time in a subject you have much interest in. The more you wrap yourself around the subject and the more you make it a part of your life, the easier it will be for you.
The calculus and physics classes I took in college were some of the most fun classes i've ever had. And I did very well in them because I really wrapped myself in it and dived to learn it. On the contrary, I've never done well in history or english writing/literature classes because I have very little interest in them. I don't put a lot of effort into them because they don't interest me.
Then again, that only applies to grade-school. The 2 history classes I had in college were done by an amazing professor with a unique teaching style, and I absolutely loved it. Passed the class with flying colors, and the exams were all essays. We had to write at least 10 pages, but 15 was prefferred, during our 2 hour exams. It was so incredibly fun though. During class he would tell us history like he was telling us a campfire story, almost. And he sometimes brought his guitar in to show us some songs people used to play. It was all incredibly inspiring....and I did extremely well.
So my point is, it depends on your interest in the subject as well as your interest in the teacher's style. There will be some teachers you perform better with and some you don't, and it all depends on how they teach the class.
