Many many years ago I somehow got roped into babysitting for a friend of Mrs D mk1.
Two young kids, a boy and a girl, running round and causing mayhem. I decided that I'd had enough.
I called them over and said...
"You know why I had to take this job as a babysitter?"
It seemed they did not.
"Well, I used to be a headmaster when one day a naughty boy, about your age, was brought to me in my study. He'd been very naughty indeed so I gave him a damn good thrashing with the cane, but I accidentally overdid it and he died. As a result I got sacked and now can't get a proper job. Now, be a good boy and girl, run along and get to bed now."
They positively sprinted upstairs to bed and I never heard another peep from them.
I'm pretty certain that that is counted as "not allowed" - but in reality it was just imparting information that you thought they might find interesting.
When I was a doing my teacher training course (I did more than one!) one of my mentors was taking a "difficult" class - aged about 12/13 and they were trying to cause trouble - I was there ot hlep out and observe
It was clear that one kid was the centre of the whole trouble
SO the teacher told me to look after the rest of the class and took the kid outside into the corridor "accidentally" leaving the door wide open
He had a chair with him and made the kid stand on the chair
He had positioned it directly under a beam across the ceiling and - for some reason - some red stains on the floor that had been there for ages and the cleaners couldn't shift
He explained - ina very loud explaining voice - to the kid that the last kid who had caused him this much trouble he had ended up hanging from the beam by his neck and the marks on the floor were cause by the blood from the hanging
apparently the Science department deposed of the body for him
The kid was positively shaking when they came back into the room
and the class worked well with no problems for the rest of the lesson and for every lesson for the next month - when they changed teachers as usual
I was not totally sure that this example was one that was supposed to be used with trainee teacher as an informative technique for application later on in our career
but I did have to be excused and go into the technicians' room for a few minutes to stop laughing
I should mention that I never threatened to harm any pupil in any way whatsoever when I was a teacher - and "what happens in the staff room stays in the staff room"!!
still - some kids etc etc