Take as many different theater courses as you can. Your interests may evolve as you learn more. Your skills as an actor will only increase as you know more about the world and how you feel about it. Work with your counselor and make sure you have a well rounded schedule. In the theater department this includes taking set/costume/lighting design so you know what your future designers work with. Take theater tech courses where you work backstage on a production every semester so you learn what the back of house life is like. Take directing so you understand where your directors are coming from. The goal is to be as well rounded and competant as you can be as a performer.
I would also suggest taking some business classes. You are ultimately your own product which you need to sell. You need to know how to do your taxes, how to start a company, how to market yourself and how to run the corporation that is "you" as an actor.
College is an amazing opportunity to get a TON of "free" classes and mentorships and work experience. Use it all, take as many classes as you can (including fencing and water polo and the occasional cultural anthropology class), and allow the experience to introduce you to aspects of theater and life you may or may not have been aware of.