I agree that teachers should have some performance standards. However, getting paid based on student test scores is unfair to teachers, because it doesn't necessarily measure how hard or effectively teachers are working.

A student who comes into the 6th grade at a kindergarten reading level is still expected to meet grade level. A teacher could work very hard with the student (with or without parental involvement, though it is MUCH more difficult to accomplish anything without the parents' help) and the student could make great progress (for example read at a 3rd grade level) but still not meet their grade level. Imagine a school where this is the norm, and not the exception (as it is in many, many urban schools). A teacher at another school could have a classroom full of kids who already meet or exceed their grade level. This teacher could hypothetically kick back and relax (not saying they would) and make more than the teacher who worked their tail off. The result is that teachers will only want to work at the schools where parents are more involved and students are prepared for school.

Of course I think teachers need to do a good job, and performance standards is a good way to check on this. However, basing it on student grades is absolutely the wrong way to do it. Student progress may be a bit more fair, but I still think teachers who work at disadvantaged schools will still have a more difficult time meeting those kinds of goals.