One event in a school

Top 3 Munich high school (Gymnasium). Some expensive item was stolen from a classroom. Thief was not found, however a teacher decided to punish the whole class who was last having a lecture in the classroom: let them clean all school territory for a week. Parents complained so this group punishment was cancelled.

In a high school I attended there were too this Soviet Army style group punishments, but I don't remember when they were undeserved or unfair like in this case.