I'm going to be sarcastic out loud during class
What's the point of being sarcastic there?
I feel we pay too much for the class
The class does seem expensive, but everyone is there to learn and you don't want to be the one who is being disruptive and taking away from their learning experience.
The point is that they can't teach me anything when I'm in such a bad mood
Being in a bad mood isn't an excuse for disrupting others though. Try to figure out why you are feeling this way and see if you can figure out better ways to make things better for you.