Randi, hitting the nail on the head

http://www.nydailynews.com/opinions/2008/04/21/2008-04-21_halt_assault_on_teacher_tenure.html

"Halt assault on teacher tenure"
"First, let's debunk a myth about tenure. All it means is that, after completing a three-year probationary period, a teacher may not be fired or disciplined without due process. The irony of the chancellor's ire in this regard is that to date, there is no accurate and fair way to use standardized student test scores in evaluating individual teachers. After all, standardized student tests were never designed for this purpose - they are meant to measure student achievement in reading and math."

And there it is right there; Randi Weingarten nailed it. Test scores are no real measure of what a teacher has taught. Too many factors and variables weigh into the picture. I might have taught an excellently crafted subject rich lesson, but if a student does not step up to the plate and do the required work, his scores might be low. Students have to pay attention and study and do homework. If a teacher's effectiveness is measured by test scores, all students in her class would perform identically on tests. It just doesn't happen. And the opposite is also true. A teacher can design poor lessons, and a student who has home access to other learning resources in the subject might ace a test.
Too much goes into the mix to evaluate teachers by a single barometer. As Randi says, stop playing games regarding student standardized test scores.