Do I have to OM at the end of class with everyone else?

The teacher will invite you to chant the sound OM at the beginning and at the end of a class. Matching your voice with everyone is a wholesome way of opening and closing classes and “making the sound of the universe” that connects everyone. You are not joining a cult by participating in the OM with the other students in the class. Bottom line: it is completely your decision. If you prefer not to OM, then don’t!