There's a lot of free time in college, if you can keep your time organized. It's very possible to (a) get decent grades (GPA 3.3-3.7), (b) learn something in the classes that are interesting, (c) hang out with friends, party like it's 1999, get laid, and (d) work on a "startup" (more like a side-project at this point) for 10-20 hours per week.
If you're effective for those "startup" hours, you can have something to show for it in a year -- maybe a business worth pursuing, maybe just an amazing addition to your resume.
In any case, going to college and working on a startup shouldn't necessarily be exclusionary, unless the startup proves to be successful enough that it makes sense to drop-out or finish your degree remotely.
