"So I guess you just deny that there are any bad teachers at all."
This is a popular retort to various forms of "Your system for evaluating teachers is a lousy system." It is a dumb retort. It is dumb in the same way the following exchanges are dumb.
Chris: I am going to cure your mother's cancer by poking her in the eye with a pointy stick.
Pat: I do not want you to poke my mother in the eye with a sharp stick.
Chris: Why do you not want your mother to get healthy?
Scotty: I'm pretty sure that one of the tires is flat. Can you get out and check?
Tony: How about I just whale all over the car with this pickax?
Scotty: Please don't do that!
Tony: So apparently you don't believe in wheels.
Ranger Smith: Help! There is a bear mauling my leg!
Ranger Duncan: How about I just close my eyes and shoot blindly in your general direction?
Ranger Smith: Aaaa!! No!!!!!
Ranger Duncan: I guess you don't believe in bears.
Let me be perfectly clear. I believe that bad teachers exist. I believe that most teachers believe that bad teachers exist.
How could we not? Apart from the bad teacher's actual students, nobody suffers for their sins more than their colleagues. We are the ones who have to pick up the slack for what wasn't taught last year. We are the ones have to take the reputational hit for Mr. Putzwhistle's bad behavior. We are the ones who have to answer the age-old question, "Why are we doing all this work when my buddy in Ms. Farkleton's has been watching movies for a month?"
You know what I don't believe in? The reformster plans for finding the offending educators. Every plan is more random and stupid than the one before. VAM?! Really??!! You are still peddling that when every reputable authority has told you it's baloney. The 10% rule (or 15%) that just starts with the assumption that there are X number of bad teachers? Private industry dumped that as a self-destructive mistake years ago.
I think reformsters have about as much chance of locating bad teachers as a one-armed blind man looking for a gnat's fart in Carlsbad Caverns. I think there are faux tin hat physicists who are closer to building a cold fusion generator and a perpetual motion machine than reformsters are to building a reliable and accurate system for identifying bad teachers.
Do I think there's a valuable conversation to be had about less effective teachers and how to best deal with them in a school system? Oh, boy, do I. But we aren't ready for that conversation, because you aren't ready to admit that you don't have a clue how to tell a great teacher having a bad day from a good teacher with a tough class from a bad teacher who probably should be a shoe salesman from a great teacher who just got randomly swept up by whatever mangled metric you loosed upon the teaching world.
You keep saying you want to raise the bar when mostly you're just swinging the bar wildly around with closed eyes and every time you randomly clobber something you cry out, "There-- it's another bad teacher!" As long as you are swinging bad metrics around like so many long-dead cats on a ten-foot pole, no teacher is going to be comfortable getting anywhere near you and your super-secret method for weeding out the riff from the raff.
It really is not that we don't believe in bad teachers, or that we think they should be enshrined and preserved. What we don't believe in is you, and your cockamamie untested unvalidated unproven evaluation systems. Until you fix that (or--gasp-- ask us teachers to help you fix it), you might as well go dowsing for bad teachers with a rod made out of woven skunk hair.