You're stuck. You're going to want a better and better camera. Just go with an entry level DSLR. Even the most basic of DSLRs is powerful... but if you spend less than $400 (I haven't looked into pricing) you will eventually. Just get a basic DSLR and a basic 28-70mm f/3.5-5.6 lens. You don't need to buy the stuff new, but you'll regret it if you don't.
True, but...You don't have interchangeable lenses, so if I ever wanted to step it up a notch, I'd have to buy a DSLR, so that kind of was a waste to buy a Powershot...I don't know, I'm still doing research honestly. xD
Check KEH for used camera equipment. There ratings on things is generally very conservative so anything excellent or better should be in very good condition. They provide a 14-day return period and a 6-month warranty. I have bought several lenses from there and been very happy with their quality.
I just noticed the phoenix -enigma suggested KEH as well so I will second that suggestion.
A dSLR is probably a good choice for taking a class.
I looked at KEH but it's kind of a small little site that's hard to navigate, and I can't find a single Canon EOS Rebel T2i camera with just the lens that comes in the box when you buy one at the store. Believe it's a 18-55mm lens, and kit comes with like the battery and charger and software and stuff.
They don't sell as many camera outfits as individual bodies and lenses - a lot of people are looking for one or the other, why tie product up trying to sell both at once? Rebel T2i. Canon 18-55mm f/3.5-5.6 IS.
Though if you have the option, a slightly older but more upmarket camera may be a better option.
- A bridge camera is little more than a compact camera with a big lens, and are much closer to those than any DSLR. That's not generally a good thing. - A bridge camera is a one-shot affair, you buy it and that's it. That's okay if you'll never need or want more than it offers, but if you're reasonably serious about photography that's unlikely. A DSLR is part of a system of bodies, lenses, and other accessories that can (and dare I say, will!) grow with you over time.
If you're going the used DSLR route (which I would recommend to most people starting out), there are probably better options than ebay - KEH.com in particular is excellent (very conservative grading, outstanding service, and a 6 month warranty), and pretty much the gold standard for used photographic equipment.
For specific recommendations, I'd probably suggest sticking with what you know if you like it, which means Canon DSLRs. Depending on your preferences, you could look for something like a 30D with 18-55mm f/3.5-5.6 IS, and maybe 50mm f/1.8, or a Rebel XT or XTi with a few more, nicer lens options.