It is true that teachers can only do so much. It is also true that they don't. I've been working in schools for years. I'm talking about schools in the projects and schools in upper end suburbs. I keep seeing the same thing. Teachers treating kids like crap or otherwise not doing their job --- and there's nothing school administration can do about it because of unions.
I should say though that the school I'm working in now has been extremely impressive (not a single bad/irresponsible teacher in the entire school), but that seems to be the exception rather than the norm.