Don't worry!! You're taking a training class to train him, right? You're not paying to bring in a dog who already knows all that stuff. Remember, you guys are there to learn!

So is everyone else, and I'm sure their dogs won't be angels either. Relax, you will be fine! (:
My advice: if at all possible, take him out to a dog park before classes (or a very very long walk, or fetch in the park, etc etc.) That's what I do for Desmond, I take him to the DP before class. Since after seeing all those dogs in the morning, he's less likely to be super amped up when he sees the doggies at Petco. He's also less wound up since he's burnt off a lot of energy, which allows him to focus better and we get a lot more done. Works like a charm for us.
Maybe work on some of the stuff before you start the classes, if you know what they will be covering. Take him to pet stores and work on his attention and keeping him under control. Even if you aren't able to perfect his behaviors, you can get a bit of a head start on his training. Maybe if you work on him seeing other dogs every few days, by the time class starts he won't be likely to get so wound up at the other dogs.
Good luck!! (: