How about physics, calculus, geometry, geometry, geometry, world history, us history, art history, biology, drama, literature, ....
Look at what is offered and try to find a way that it applies to what you want to do. Advanced english classes that might give you the opportunity to work on or study story telling would be great. To me, the thing that sets the work of pixar apart from a lot of other companies is the story. Look at these:
http://www.pixar.com/shorts/index.html
The story stands the test of time even as the technology that produced them becomes dated.
If there is a drama class you can study acting and lighting. There is probably no substitute for having hands on experience with lighting.
If there is an advanced biology class you can probably study how organisms work in depth. That would be a tremendous help if you are an aspiring animator or modeler.
Calculus and geometry will be invaluable if you are interested in writing shaders or in rendering theory and methods in general. Linear algebra would be fantastic if it is available.
If there are no art courses left that you haven't taken then perhaps you could arrange an independant study course during a study hall or perhaps for credit.
I think anthropology could be helpful if it is available, from a story telling point.
Do you have any ideas about schools that you are interested in? You might be able to contact faculty members or admissions to find out better ways to direct your studies.
Did I mention physics and geometry?
Good luck,
ww
And please forgive my spelling