Why do you think it is so hard to remove bad teachers?
I once encountered a bad teacher at my kids Junior High, she was the worst. The class he took was a typing class. As it turns out, I could have taught the class better than she could have.
We had a fundamental disagreement. By the end of the course, the kids were still looking at the key board, and pecking with their fingers. She told me there was not one "right way" to type. I was like, WTF?!! There sure as hell is a correct way to type. It is why the letters are arranged in a certain way on the key board. It is why, on every key board, the "j" and the "f" have raised ridges or bumps on them.
She wouldn't hear of it though. She told me it is up to the kids to determine the style of typing that they would choose.
Now my son is in High School, I encountered this useless educator again at a parent/teacher conference, she is still in the system, still teaching. This time she was teaching a class called; "Post secondary Prep." It is the most useless waste of time. Hers, and my sons. He reads a book and journals about what he read. Then she reads what he read. I asked her, do you correct spelling, grammar or look for meaningful connections about the kid's reading? She answered, no, she just makes sure they read something and wrote about what they read, that's all. She doesn't comment or mark the papers at all.
Useless.