To be honest though I don't favor any standardized test as the sole method for evaluating teachers. I don't think test can replace the judgment of a qualified principal but instead should be used as a tool for principals to evaluate teachers. If a teacher has under performing students the principal should investigate the problem and evaluate and correct the problem even if the correction is to remove the teacher. Does this mean that occasionally a teacher will be unfairly fired, as happened all the time in the real world? Of course it will happen sometimes and that is sad but since the option is to force some kids to have bad teachers I choose the kids. Schools which make a habit out of firing good teachers will under perform and new people can take over who will run it properly.

The problem is there is no perfect system that will 100% of time show which teachers are good and which teachers are not so good but the union wants to demand that until such a system is in place there should be no evaluation of teachers at all. Teachers union have two jobs, get politicians elected who will support them and protect teachers jobs, in that order and looking after kids is just lip service.

Which system is used does vary but in most them a teacher may get "dinged" but in very few can they be fired without a long drawn out court filled process. It wouldn't surprise me to find out the city with the worst schools in the country has the worst method for evaluating teachers. I don't believe any system is firing teacher based solely on how well their students perform on standardized test.

You can argue against the blame the teacher approach but the success of the charter schools shows us the blame the school method is valid and instead all you are really doing is saying "don't judge the teachers blame the parents and kids". The problem isn't who to blame but how to fix it and without accountability for under performing schools and the power to remove under performing teachers it doesn't matter how much money we spend our schools will fail. A bad teacher won't become a good teacher for more money and a good teacher will not be attracted to system that refuses to reward their excellence and forces them to work losers who are just warming chairs and enjoying their power over kids.

What protects teachers from being unfairly fired? Simple, their skills and the demand for quality teachers. If principles are judged on school performance they will do whatever they can to keep the best and get rid of the worst. Why do qualified professionals need unions to keep them from being fired?