I take my hat off to teachers. I really don't know how you stick it these days, as many of the posts on this thread are hair-raising.
I am very supportive of schools. It seems like an impossible job these days. In 19 years I have had 3 DDs go through school. In all of my dealings with their schools I was polite and civil.
In all of those years I never had any problems with a single teacher, all were helpful if I wanted to ask or clarify anything.
I did have an issue with one member of admin staff at secondary school, who took it upon herself to go around the school in morning registration time with a tape measure recording the length of girls' legs against their skirts (including my DD), then loudly talking about those vital statistics in front of the whole form. The form tutors had also questioned what was happening and had themselves reported to the headmaster though. He immediately put a stop to it and then phoned to apologise to all parents who had emailed to question it.
Too many parents take their children's words as gospel. It always pays to check the other side first, if there even is one. Children often do embellish things, some even making them up entirely. Chances are that little darling is not as entirely innocent as they are trying to make out to mum and dad.
There is never any excuse for threatening behaviour, verbal or physical. Support the school. Then if you really do have an issue they are much more likely to be helpful.
My parents were teachers. They are in their eighties now and long retired. I don't doubt that they could add many stories to this thread but they don't do computers or internet.