I will never forget this incident:
It was just after lunchtime at school. I was in the 4th grade (10 y.o.).
The classroom door was open so the kids arriving from play time (including myself) walked in without waiting for the teacher.
Written on the black board in big chalk letters was "F U C K".
We went apeshit; "OMG," (catholic school) "someone wrote FUCK! Mrs Rafferty is going to fuck up whoever wrote that!"
We started playing detectives, getting the usual trouble makers to display their handwriting on the blackboard for comparison.
Mrs Raff walked in and before we could finish "Mrs RAFF!!!! WE CAME IN FROM LUNCH AND SOMEBODY HAD WRITTEN F...",
she had already wiped it off an was acting as if nothing had happened.
We all calmed down immediately, expecting an afternoon of high drama but instead returing to our school work in a daze.
She was a good teacher.