The other week, there was a fight in the hallway between two middle schoolers. I was disappointed that they weren't able to talk out their differences and had to use violence. I talked to another student who had seen the play and also witnessed the fight. He reassured me that he remembered the lessons from "just kidding" and it made a difference to him.
The reality is that we sometimes forget lessons taught to us, and most need to be reminded many, many times until we can put life lessons into practice. That is a part of growing up, and we all make mistakes.