Maybe this instance is fake, but this does happen: my primary school teachers went as far to refuse that negative numbers exist.

She got angry if someone hinted at them.

I got this in school, it happens. Or happened in the 90s.

I literally had a teacher once "correct" me for saying the area of a circle is πr² instead of πrr. I was told "you're not wrong but that's for future classes". On another class, I had a teacher correct a short story by removing repeated words, whereas I used repetition for emphasis, but used a comma instead of ellipsis. Think "I saw it, saw the thing" instead of "I saw it... saw the thing". Both was in early elementary, no higher than 3rd grade.

So, believe it or not, things happen to other people even if they didn't happen to you.

The worst thing about calling this fake is that it's not even unbelievable, it's a perfectly possible and mundane thing that most likely happened to millions of children as they grew up, yet everything in the internet is fake, right? No one just happens to record people for no reason, no one's smart enough to make funny jokes in the spur of the moment and get a reaction from strangers.

EDIT: Added context.

I went to a lot of different primary schools (UK here, that's up-to-11-years-old) and there absolutely were ones where this happened. There were also good ones.

it happens with bad teachers, and "good" parents will take the students side when the teacher's being an idiot.