Snitching
In my childhood days, when one of the classmates secretly had done something bad, it could happen that we all had to stay in the classroom after school hours. "Everyone keeps sitting in ones chair until the culprit report himself!" said the teacher, with which he unleashed a small psychological war.
Possibly he considered this as a lesson in loyalty. Mainly a lesson for the guilty one, because now he or she might feel the undeserved punishment of 29 innocent fellow kids. If the kid was a brat, it wasn't bothered at all. In that case, the stay after school was a lesson in betrayal.
The only thing the teacher needed to do was waiting, until one of the other kids explodes in impatience and would shout out: "Yes John, say it!!!"
But ... 9 times out of 10, it was just a lesson in respect for the teacher ... because he only had to look at the faces of all the children, who automatically did stealthy glances on John. It was incomprehensible to us that -after a few minutes of deadly silence- the teacher apparently had found the perpetrator and could sent home the rest of us.
We, in return, were baffled how the teacher had identified the snitcher.
I've used this technique with my own kids. It's been highly effective. Is this photo of YOUR own school? I want to go to this school. Looks like a great bunch of happy kids. Hmmm, I think I see who the culprit is.
Whaha, and that's why Dads have secret powers too.
Yes, this was my school in the Netherlands in 1974. The 4 guys on the left mostly were the troublemakers.