I need to keep my mouth shut.

Every other Tuesday morning, I lead an English conversation class to a group of about 10 retirees. Boy, do they like to talk...and not in English, of course. They're a close knit group. They're very nice and a lot of fun to be with. I've been having a hard time keeping them on track to speaking only English during the hour and a half that we spend together. The other day, a friend recommended that I write a list of everyone's names on the board. Each time I catch them speaking French, give them a mark next to their name. The person with the most marks at the end of the class, must buy coffee for everyone. We actually did that during my French lessons back in the day so I decided to try it. I added my name to the list too. The class was incredibly quiet today. Too quiet, in fact. I didn't like it. Who's buying coffee for everyone for the next class? Me. I broke down from time to time when they didn't understand a simple word that was impossible to describe to them in English so that they'd understand. I was weak.