Everyday, these boards are filled with parents complaining about their DC's school. Yes, some of the complaints are justified, but many are not.
As far as I can see, most people complaining are not qualified teachers themselves, so probably have little understanding of the rules and procedures teachers (and TAs, heads, etc.) have to follow in order to do their job correctly. I think a lot of people on here undermine teachers and don't respect the education and skills that they have.
I read this article today: www.theguardian.com/teacher-network/2015/may/30/secret-teacher-astonished-some-parents-complain-about
From reading this and the comments, it is clear that this is a big problem elsewhere too.