I managed to stay on the Dean's list while still playing tournament smash, and having a g/f and an internship.
Of course, it was all really a product of scheduling. I'm an afternoon person, that is to say I cognitively function a lot better in the mid-late afternoon. So, I made my classes accordingly.
However, my biological clock kept getting me up around 10 or 11. With no class until 2, and being done at 5 or six, I was able to smash every day from 10/11 to about 1:00. I'd go to class, come back and get dinner and get some work out of the way. On weeknights, after that I would smash. On weekends, I wouldn't touch it. My internship was a couple days a week for only a few hours in the early morning, so on those days I didn't get my morning smash in.
All in all, its the exact same as doing ANY 'extracurricular' activity in college: Intramurals, Clubs, etc. Just 'schedule' things that you can (e.c's and such) and then work around what you *can't*. But like everyone else for the most part has said- school definately comes first. Dont go to a tournament if ya dun ave the $ of time, or if you wanna spend time w/ your gf that weekend. Really, no one at the tourney your friends with will hassle you. If they do, they need to seriously get a life.
Time management, prioritizing are the keys.