More Joys of Teaching English

So I have a new junior high class and they stuck two classes together. From one of the classes are three junior high boys and one kid who's probably in fifth grade. Anyway, the three boys, John, Jerry, and Ken know an impressive amount of swearing. As I walked by, David, the little boy who's also kind of their mascot, said, "Teacher, I am clean. I am in elementary school. I am clean." The second time he did this, I was sort of irritated but also kind of amused, and said, "David, if you are clean why do you have to tell me you are clean. If you are clean you don't know what dirty is." At which point Jerry chimed in with, "Yeah, we are dirty. We are in junior high." This didn' really help matters. David didn't really know what to do with this conundrum, and said, "My little name is Mr. Clean." At which point there really wasn't very much I could say.