At some point you have to stop wondering what is wrong with the teachers and schools and start wondering what is wrong with the parents who keep their kids in these schools and tolerate this.
When I was a kid the standard was that if you got in trouble in school, you got in trouble at home. But if a teacher had pulled a stunt like that she would be lucky to live long enough to get a trial.
The standard should have been, if a child gets in trouble at school then you find out what happened and use your own judgment. Instead the secular adult world, worshipful positivists that they are, opts to hide behind “the institution is always right,” thereby discrediting itself. Whoever it was who said the government schools will destroy the civilization that gave rise to them was onto something.