My comment that you copied was based on personal experience. It's unfortunate that you choose to lash out rather than read and understand. Perhaps your own incompetence was protected by a union at one time?
I have had conversations with three different principals in our district who admit the same thing. These conversations happened after we (as individuals and in groups) sued (and threatened to sue) several teachers for abusing students and using grades to punish them and their parents. Did you know that the school administration in our district cannot override any grade a teacher submits? Can you imagine how a corrupt enterprise like this uses this leverage to produce the desired behavior in students and taxpayers alike? I am painfully aware and knowledgeable about the problems of public education, and how lousy teachers don't teach, abuse, and then indoctrinate our children, into accepting social justice and collectivism without question.
Our district is fairly affluent so the lack of parent participation in the process isn't as widespread as it is in more urban areas. Yeah, parent neglect a serious problem, but it is these same people who promoted the ideology that has destroyed the family unit in this country while engendering the belief that it takes a village (government) to raise a child. The entire system is corrupt and wretched, but the teachers played, and continue to play, a huge part.
Teaching in our system is an easy job with the highest pay in the state and a pensions system the private sector can only dream of. Even though the government ties their hands and dictates far too much, they have no problem finding teachers. I know it can be very different elsewhere. They made their bed and now they need to lie in it. It must be nice going to work every day not having to worry about competition or producing results. It's the perfect job for people who aspire to be dead weight. It can also be the perfect job for people who want to make a contribution. If the union (and the people who protect the union) would get the hell out of the way (along with apologists such as yourself) we could make sure we have more of the latter than the former. That would make more than a little difference.
Your comment about "it must be nice going to work every day not having to worry about competition or producing results" is a semi truck load of baloney. Teachers are constantly being harassed for their grade stats and whether their lessons are in line with the teaching methodology currently in vogue. There is currently no room for teachers who want to be mavericks and teach the way they think they should teach, to "make a difference". Such teachers have a special name: unemployed. Your whole discussion is about some alternate universe, not in line with current Earth reality in large cities.
Not all school systems are created equal.