I was hired out of school before I could graduate (BA in Game and Simulation), so I can’t speak from first-hand experience. What I have seen is a lot of people who dropped out while thinking they knew enough about game design to start on their own. Those people didn’t make it, but the people I have seen be successful were either hired out of school, graduated or were working on a game during school that they later published while a student.
Anyway, that’s my two cents.