Not all teachers belong to unions (I taught in TX, no teacher's unions, thank goodness) and it's simply not true that it's almost impossible to fire a teacher. At least where I taught, we were there with a contract each year. According to my contract they could fire me for cause (which means, whatever they felt was cause) and I've known teachers who simply were not offered a contract for the next year.
I'm sure it's a state by state.
I do agree there's not much incentive for excellence as pay is based on years of service. I guess some of us are just masochists.
susie
In Hawaii, it's a pretty simple contrast.
The private school teachers are non-union and the public schools are union. People pay a lot of money to get their children into the private schools. The pay for teachers at private schools is lower than the public schools -- but they have individual performance contracts and enjoy the freedom to teach. Most teachers' objections to schools and teaching as a profession are really the arbitrariness and stupidity of union rules.