I must be desperate for your attention

You know that little hand motion wherein you concoct a circle out of your pointer finger, and thumb, then insert the pointer finger of your opposite hand, and gesticulate back and forth? When I was in fifth grade, a classmate of mine acted out that little pantomime in order to shock and (or) bemuse the rest of us. One of the girls instantly shouted out,
"Stop it, that's dirty!"
Up until her outburst, I honestly had no idea that the crude sign language was a representation of coitus. I felt that the circular portion combined with the rhythmic insertion of a rod was just a mock up of the act of cleaning a toilet with a brush. Or perhaps, plunging a toilet to relieve a clog. Some children were embarrassed by bodily functions, but I was taught not treat urine and feces as comedy material, so they were not to be considered "dirty".

I attempted to quell the mob and diffuse the situation. "Don't be a baby," I said "My mom makes me do that all the time."
Pandemonium ensued.

In conclusion, kids say the darndest things.