Try again....
I get that there are some parents like this. And I can see that it must be really difficult for teachers and school staff... But....
I think that some school rules and sanctions are arbitrary and foster resentment. My example above... A child is screamed at in front of his peers because he struggles to transition from one activity to another. Another child is persistently called names and excluded by classmates, but they are told that they should deal with it alone and there are no punishments or sanctions for those children. A parent forgets to sign a form and return it, the child has house points removed, another child lifts up a girls skirt to look at her pants and he is told to stop being silly and sat back down next to humiliated girl.
My point is that in my experience, (I do work in and out of schools), it is when arbitrary rules are applied and then administered in a sporadic or unpredictable way that pupils and parents begin to feel victimised and a power struggle ensues.
Yes... Parents should support a teacher's authority. I recently made encouraged my son to write an apology letter to his teacher after he got 0 marks for a test because he asked a question during it when he had been specifically asked not to. This is a fair rule. He has fair warning. In the future talking during a test could have more serious repercussions. However, this support should not be at the expense of a child's mental health and learning. I did speak to the school about Miss. Scream because I believed that her constant screaming highlighted a training issue at the very least and a temperament unsuited to teaching at worst. My child was quite simply not learning.
I also know that one of key ways or children learn how to behave is through modelling the behaviour of the adults around them. Teachers are not exempt from this. If a small child has a teacher/parent who shouts and punishes when someone does not do what they want them to, how are they going to behave in that situation. What are they learning about dealing with conflict? How do they respond to it as a child, but also then as an adult?