In part I agree with you. Tenure (which here in Spain is different: all public workers that got their job through examination can't be fired!) is a big problem. There are a lot of amazing teachers (I've had a lot in my life, since school through university), but there is a lot of lousy teachers (also had a lot of these) that do nothing and can't be fired. And the ones who love teaching (a few of my friends are math teachers) have to suffer more or less what the article says. Education always takes the blame, regardless of the quality of the teacher. Also, they have an increasing responsibility: parents no longer "educate" children (how to behave well, be quite, listen, be respective), it is something that now school teachers and HS teachers have to do, without any level of help from a lot of parents. A simple example, is that when a child gets some kind of "fine" (bad grade, a written note to her parents, whatever), most parents blame the teacher and don't believe "their little child" misbehaved.
Are you sure that's "most parents"? The ones that have a good yell at their kids in the bedroom for their behaviour are the ones you won't hear about, and I suspect they're the majority. I know I don't expect schools to rear my children.
I don't know of a study that has quantified the "most" allegation. But what I have heard from relatives who teach (or resigned from teaching) in public schools is that a large enough number of parents take this approach and seem to come to the parent-teacher conference with the "my great kid is entitled to grade X" attitude... that teachers' authority/professionalism gets undermined.
Even worse when administrative does not have your (teacher's) back.
If you doubt that the Peter Principle still applies, spend some time in faculty meetings and check out the admins. There are exceptions, of course. But IMHO (observation) the "No more A-holes" rule is more honored in the breach than the observance.
