Punching a guy in the face during class might be a little overwhelming, plus your instructor might get mad. If they go to slam you you have to grab on to their legs, especially if you have the triangle in.
Obviously some people are retarded and just do not have a clue. If that is the case just choke them unconscious or something. When they ask why you did not let go just say you did not tap. They will not remember since they just went unconscious.