we had great luck with berda.com for regular t-shirts the prices weren't too bad, the turn around was good, the proofing system worked well, plus we got a free banner one year... (these were screen printed shirts)

it is nice to stick to a local company and keep that money in your local economy. try your local yellow pages (if the school doesn't give you copies, the library will have it) it will probably be more accurate than an internet search.