Keep in mind that if you have a weaker science background than most Caltech freshmen, the first two terms (during which everyone will be taking close to the same schedule) are on pass/fail, which gives you time to even the playing field without a lot of stress over grades. I seriously struggled with passing Ch 1a, Ma 1a, and Ph 1b, and I'm now doing well in one of the harder majors here (physics) with a good GPA and cool research, looking to get into top grad schools. What's important is that you make sure that you *learn* the material reasonably well even when you're not getting a grade for a class. Also, absorbing the intelligence of your brilliant peers over the course of two terms helps a lot.
