DottyMo made a really good point about the volume in the classes. When my son was 11 we went to Cancun and to the Rainforest Cafe. We had never been to one, and got to experience the animals moving and the sounds of the jungle. We sat and ordered, and as is often true in Mexico, the order took a while. My son started getting antzy and wanted to go--we had ordered and I told him we would get it in a few minutes--my usually calm composed son, burst out crying. He couldn't take that much stimulation. Sometimes we have some issues that just don't come up until something like your class comes around. I'd suggest ear plugs. They don't have to be obvious. Even filtering out a bit of the noise might be enough to let you relax. Usually you can still hear the teacher, but if you can't, tell her why you are trying the earplugs, and if she would just touch you on the shoulder, or come stand near you, so you can take them out and listen to her instruction. Most teachers want you to succeed, and will work with you on these small things that help to make a good class.
I've also had a class recently where I got the pattern early. Well, I chose my fabrics, and sewed and cut out part of the project. It was far from finished. If I didn't think I understood, I would stop, but sometimes getting a jump on the class gives you a head start, and puts less pressure on you to preform. Try to figure out what is making you so nervous, and see if there is a work around.