The first comment in the OP also tries to make the point that it's impossible to tell just how good a teacher is. I claim this is all crap. The same problem ex

The first comment in the OP also tries to make the point that it's impossible to tell just how good a teacher is. I claim this is all crap. The same problem exists in almost any non-manufacturing job; certainly in the field of software development. We've got piles of bad metrics, like KLOCs (about which, the less said the better). We could count bugs, but different systems are prone to different levels of bugginess, and when we're all teaming up, it's not necessarily practical (let alone advisable) to "blame" someone. Yet by and large, we do a pretty good job of determining who are really good, and who aren't. You mention that the standards themselves are, in some cases, bad. That may be true, but you should be trying to get out of such a district ASAP. The fact that they can't get good teachers, and the fact that the parents are hammering on the door because the kids aren't learning, should force change -- but for the fact that the system now gives parents no alternative. It seems like the teachers' unions are hanging onto a fig leaf of rationalizating, but it's really a case of the perfect being the enemy of the good. We could do a lot better than we are, but we're not allowed to go that far because it may fall somewhat short of perfect. But look at the bigger picture. What's a more serious failure: (a) not giving a teach a raise quite commensurate with what he/she deserves; or (b) not educating a whole classroom full of kids because they're stuck with a lousy teacher?