Under the “Race to the Top” guidelines, California may be ineligible for federal money because of a law pushed by the teachers’ union that prohibits the state from linking together student test scores and teacher performance. While there are a lot more issues at stake here than just test scores — e.g. state vs. local control seems to be an issue here — I’m not sure there’s anything inherently wrong with using student test scores to evaluate teachers.
There are certainly evaluation systems in which teachers are punished for poor test scores because they happened to, by chance (or politics), get stuck with the dumb kids. This doesn’t all systems suffer from this problem though. For example, let’s assume that a student’s academic performance can be tied to three things — teacher performance, overall school environment, and things beyond the school’s control (e.g. inherent ability, home environment, etc.). We can reasonably assert that things like ability and home are relatively constant over several years. We can also state that the overall school environment should have a roughly equal impact on all students. Based on those assumptions, we can control for the individual influence of a teacher in any given year by simply evaluating a student’s performance in context of other students in the school and that student’s performance relative to previous and subsequent years — something any statistician worth his or her salt can do.
Controlling for a student over time is especially interesting. It actually creates an incentive to grab the worst students — because when a student is already at the bottom, he or she can only go up.
Now, these assumptions aren’t perfect and don’t capture everything. For example, cutting ESL will have a greater impact on teachers whose students don’t speak English as a first language. The point is, however, that these things can be controlled for. Decent administrators and statisticians can create fair teacher evaluation systems by linking teacher performance to student performance. It potentially rewards those teachers who go above and beyond to help students not only in the classroom but outside the classroom as well.
I think the objection of the teacher’s unions are that, while it is possible for test scores linkages to be used fairly, it’s very possible they’ll be used by dickhead administrators to unfairly bludgeon teachers they don’t like for political reasons. That’s akin, however, to a lieutenant not giving his soldiers hand grenades because that’s just one more thing they might frag him with. In other words, if that’s your biggest concern, you have other problems to worry about.