Anyone who argues we do is not seeing the whole picture. I am in PA where teachers are paid very well. They even admit it when they have to. You would think the good teachers would want to get rid of the bad teachers. I am sure a few do, however the unions are to attractive. I have seen people who consider themselves anti- NEA join. They will have a hundred excuses why. The real reason IMO, it makes teaching easier and offers benefits .. We need to reward people who understand the delicate nature of child development and do not humiliate children into conformity. We need to reward students ,and not suck the joy of life out of them. I have no stats on that... but that is what I see.
There will always be problem kids and problem parents. We will always need to hire people to deal with them. Afterall, it is the NEA who thinks all people are exactly the same, or should be, and should be lumped together based on age not skillor ability. People should not go into teaching thinking that while they join the NEA, they are going to make a difference in education. They just are not. They may make a difference with one or two kids, or a classroom of kids if they are compassionate. And that is very worthwhile. But they should not scream about how unfair everything is while they are at it.
When the NEA is gone, and they will be within the next 15 years, good teachers will see the rewards. Job conditions will improve and kids will learn again. Why some teachers fight , I think, is because it is scary to be without big brother who has told them how to feel , what to do and how to think for so long. ( I also don't have any stats on that)