ParentOfOne
I don't think the school ever said much other than they used disparaging language.
The school thought that the parents had done enough to go to the police for advice, this is highly unusual for any school, as is banning parents from the school grounds.
Neither is a step that schools take lightly.
You keep pushing for answers that nobody can give you
You say
"The one things that is clear from this thread is how stupid, arrogant and biased most people are."
and
"I have had bad experiences with schools, but I don't let that taint my judgement, I don't jump to a biased conclusion. I suspend judgement, because I don't know, and neither do you."
But it seems that you do have the same cognitive bias that you say other have and that you don't suspend judgement.
I can only speak from my experiences of being a teacher and working in schools.
Schools don't always get things right, but things have gone very wrong if the parents are banned from the site and some of the responsibility for that must remain with the parents, Because I have seen parents give out some serious shit including threats of violence and not be banned form the site.
If you have read this far well done because here is the twist.
I honestly believe (Just my opinion) that if the parents were just getting under the skin of the teachers then very little would have happened, but they decided to have a go at the SLT and governors, and that in my opinion is why they got banned and the police asked for help. (but that is my bias, and my experience).