True story (I'm a retired high school teacher) - one day at the beginning of class, everyone, everyone was standing up and horsing around. They weren't paying one bit of attention to my plea for order. Finally, I said in a loud voice, "Sit down!" They dropped in their spot and sat on the floor in unison.
It was hysterical!
It was staged. The rascals.
We really did the synchronized turn the desks around thing to a substitute teacher when I was in high school. We caught hell for it from our regular teacher when he got back, but it was worth it.
Teachers have my admiration. You certainly have more patience than I do.