Actually muddypaws, at the school district that my mother works at, it's become apparent that they're attempting the same thing. One of the principals is basically trying to run certain teachers out of the school system to make way for the younger teachers. They'd be cheaper, but mainly he wants to get rid of the ones he doesn't like.
And get rid of the ones that are more outspoken that would challenge him when it comes to poor policy and bad ideas. This guy's a prick, but the superintendent doesn't have the balls to do anything about it right now. The amount of politics and bullshit that goes on within these school systems is insane. Getting rid of the Union would just make life worse for a lot of teachers that have done nothing bad or wrong... they just caught the wrong side of the wrong person.
'sides... Public schools get all the leftover that private schools don't want. Hate to say it, but you'll see a lot more disabled/handicapped children in a public school than you ever would with a private one. Think charter schools are the same way (not sure though). The idea is that public schools don't get to choose who comes into their system. So to base them off of how well kids do in their classrooms... you're always going to have some that will underperform. This should reflect on the teacher? You can only do so much when the kid, nor the parents, really seems to care.
And unfortunately, more and more nowadays it seems the parents don't care, or have the "My child can do no wrong" mentality that is just as destructive. It isn't always the teacher's fault.