In principle, this is true, but you want to reward individual performance, and not all teachers as a group. This is impossible with the current system. After five years of teaching, Utah teachers are awarded "continuing status" which is essentially tenure, and they'll never be fired for poor performance in the classroom, only egregiously bad actions. The worst teachers sometimes get shuffled around from school to school. It's called "the dance of the lemons." 

It would be nice if we had a system where outstanding teachers had the ability to be given raises beyond union scales which are simply based on the number of years the teacher has been employed, and earn high salaries based on performance. It would be nice if administrators had the ability to get rid of poor performing teachers and bring in new blood until they had a top notch staff. But it just doesn't work that way. 

Our education system isn't as good many developed nations, and it isn't for lack of spending. Curriculum is a problem, but you also have to lay some blame at the feet of our teachers. And teachers consistently opt to preserve the union system we have, instead of a system that strives for excellence. For all the rhetoric about teachers being the most valuable members of our society, they consistenly put job security over quality education.

I also don't like the idea that teachers are automatically bestowed with a mantle of virtue simple because they are teachers. What makes a teacher better than a guy who works 60 hours a week in the hot sun as a carpenter for $12 an hour to feed his family? My mom worked hard in a lousy clerical job for years to help pay for our clothes and food. She didn't get a pension, health care, or much vacation. Do I think teachers are better people than her? No.

There were three teachers in my elementary school who later went to jail or were accused of child molestation. Two of my kids have mild learning disabilities, and most of the teachers they've had have been a nightmare to deal with. Some I would say are just bad people who have no business being near a classroom, others are simply incompetent, or don't want to be bothered with a kid with special needs. The good ones are priceless, but the current system simply won't allow our schools collect those ones. Paying teachers more money in the current system would only be throwing money at the same bunch we have now.