The procedure for letting the kids know that recess is over is for one of the teachers on duty to blow a whistle. Everybody stops playing and lines up with their teacher to come back inside.
So today, while walking out to recess, a kid noticed something about his teacher and had a question.......
Kid: How are you going to know when recess is over if you don't have a whistle?
Teacher: Well, I have a watch. (She puts her hand on her wristwatch)
Kid: Yeah, but a watch doesn't make noise like a whistle.
I need a weekend to think about this.