Commercial games are big business these days, and like movies, there is a whole range of different skills that are needed - writers, graphic artists, sound engineers, musicians, programmers, directors, even actors and motion-capture teams. There are specialized colleges teaching these skills, but I think a good place to start is hacking on your own. Learn to write simple little games, learn what makes them fun, learn which parts you enjoy doing. If this sounds overwhelming, well, it's not easy, but people write "seven-day roguelikes", that is, complete roguelike games in a week. There's also a one-week game competition for writing games in python with pygame.
As for what courses to take in high school, I agree with damnpercy: math and statistics are very important; a programming class if you can get it. I'd also recommend art and creative-writing classes - even if you're more interested in designing the rules, being able to make your own art and write text will help a lot in your learning games, and may be essential even as a commercial game developer.
But if this interests you, and it sounds like it does, make a hobby of programming. I'd recommend learning python, since there's the wonderful game toolkit pygame and a community of people writing small games. Flash might also be a good place to look for writing small games, though I think python probably teaches you more about using a "proper" programming language (that is, one that can be extended to large projects).
You might also find it interesting to pick a game you like and find out how to write "mods" or extensions to it - this lets you get something playable very quickly, and you can learn interesting things about level design very quickly.
