Sabra at Tailer Park Paradise comments on "... the odd dichotomy I constantly see from any number of my teacher friends on Facebook":
1. Teachers are the bulwarks against stupidity and take extra special care of your precious snowflakes and teach them all they need to know to make it in the world, so you should pay them a lot more than they are already paid.
2. If a student fails in school, it's not the teacher's fault but someone else's. It is therefore unfair to judge a teacher on the performance of her students and want to fire teachers whose students underperform.
Again, I say: you can't have it both ways.
I sincerely doubt that there are any individual teachers who hold both views simultaneously. I think it is far more likely that good teachers argue from POV #1, while bad teachers argue from POV #2... and teacher's unions argue from whichever one they think will suit their interests at the moment.