I was once running a review session for a history class that I was teaching, and two of the students kept interrupting and talking over me (and the other students). I was handing out fortune cookies for good answers (what? that's what I had). At the point that I started to get frustrated, I gave a minor rant, "this is an optional, after-school thing, if you don't want to be here, then go, but if you're going to stay, stop disrupting the meeting." The kid guilty looked down, then read the fortune cookie that he had just opened. His jaw dropped, he showed it to the other student who had been disruptive, handed it to me, then sat down quietly.
The cookie said "Respect your teachers"