We are having a Halloween party on campus from 11-1 with best costume awards and snacks for our campus awareness day on Friday the 30th. We typically have about 50 people that dress up for the contest...and I go to a community college. So, depending on the size of your school, check to see if there's something scheduled so that you can take part in it and if you have free time, then head to that?!. You might stand out a bit much if you dress up on the 29th?!. But then again, standing out isn't always that bad!!
I wore my werewolf mask and a necklace of little plastic jackos that would light up to campus last year. Took the mask off during classes of course...and was the only person I could see to have done anything of the sort ...but yeah, it was awesome. As long as you're not being a distraction during a lecture or wearing anything lewd/obscenely gory/I'm sure I'm preaching to the choir here, you should totally do it and I don't think you'll have a problem.
I agree with Brombones, don't worry about what anyone else thinks just do what you want to do. Besides, dressing up in your Halloween costume and going to school one day like that can't be any worse than the way some dress every day and go in, look around sometime.