Well, the farthest I got in High School was Pre-Calculus. It would be a good idea to take Calculus your last year in High School, if you can. I currently attend a CSU, and I have to take the following math courses for my CS major:
Calculus I -- (passed already, failed once)
Calculus II -- (failed once, currently taking again)
Probability and Statistics
Discrete Structures
Linear Algebra
You'll also have to take some physics courses as well!
My gpa in high school was 3.76, and currently 3.0 in college. I'm in 2nd year..
Programming, the main focus of CS, is really tough though; for me, atleast. As many people have said it before, You either get it or you don't. It also tends to get boring at times.. But it depends on the person. If you're really interested in computers as I am, it is interesting as well!