I'm a sophmore in college right now, and all I can say is don't try and spend the majority of your time play Starcraft. I did that my first semester and well, I got good at starcraft I can say, but my grades suffered for it. Sophomore year I played a lot less, but kept up with the game and had really good grades.

Honestly, I'd make a "schedule" for starcraft, I'd have certain periods of your free time where you say I can play games now, but at these periods of time I have to do school work.