I obviously don't know where you go to school, but some smaller universities are so technologically ignorant that they only allow port 80 plus the other 6-7 well-knowns through. You can ask to have it unblocked, but some universities (mine, for example) won't unblock IRC ports because they're afraid it will be used for file-sharing (which in the US would subject the university to legal action).
In my case, using a web-based client (such as mibbit) worked in the end, and it's what I had to do for a year while I was in the dorms (it was my only complaint though - horray for fiber! I had 50meg download at one point =/), but you run into the problem of SWC's IRC server only allowing a few mibbit users to be connected at once, so if there's a lot of Combiners online from work/other places that block IRC already, you may be out of luck (unless they decide to raise the number of allowed connections, like they've been asked a few times before).
Alternatively, using one of the alternate ports worked for me intermittently, but only until the university caught on and blocked them as well. Sigh. So you could try that first, too.