F bomb

Has anyones child (mines is 6) dropped the f bomb in social settings like dance, class etc.? I feel like a failure bc we have been working on behavior. The moment I chose to watch my oldest daughters class this happened. So I don't know why happened and wasn't told much at all. I also don't like how it was handled. A patent found me and told me my daughter was in the hall crying. So I withdrew her from the class and of course had a talk with her.