I really shouldn't say anything: I have too many friends who are teachers.
The much-publicized film "Waiting for 'Superman'" made the specious claim that "bad teachers" caused low student test scores. A Newsweek cover last year proposed that the key to saving American education was firing bad teachers.Yes, I've know how much public school teachers hate "Waiting for 'Superman'". I haven't seen it, so I won't defend it. But isn't it just a bit disingenuous for teachers to claim that they have nothing to do with students' low test scores?
And how can anyone say that it's a bad thing to fire bad teachers? Are they blithely asserting that there are no bad teachers? (I never met a teacher yet who thought so.) That there is no way to tell? (Likewise.)
In every other service career it's expected, in some cases legally required, that there will be some kind of evaluation of job performance. Criteria for success are clearly defined, transparent to the consumers of those services, and publicly available. I can't think of a single reason why teaching should be exempt from this. This is the flip side of desiring more commitment from your students' parents: You have to be able to prove that our children are actually better off spending eight hours a day with you than being home schooled, or even being locked in a cage in the basement.