Here's a junked-up diagram of the legal proceedings around the dismissal of one Colorado science teacher, who apparently refused to teach the curriculum mandated by the school. I'm not saying that the teacher was right, or that Colorado's laws are appropriate or not. I would note briefly that the union's role in all this is not stated, so is presumably minor. Also, you'll note that there is nothing here about performance or student achievement, just compliance with administrative orders.
I don't think it is too hard to see where this kind of thing goes if teachers start losing money and/or their jobs under performance evaluation. Let's say the teacher in the above case relents and teaches the proscribed curriculum, and his students' scores go down, because the curriculum isn't aligned with the tests, isn't backed by good research, the district doesn't actually provide the resources required by the curriculum, etc., and he loses money or his job because of that. Then you've got just got a different lawsuit. Except this time, if you've changed the administrative law around instead of a hearing you have a tort and a jury trial. Maybe he'll subpoena the superintendent and the head of curriculum of instruction. How much money are you saving then? Who's gonna win that one?