NYC is publishing its teacher data reports today for 4-8th grade English and math teachers who have taught at least 2 years out of the last 4. Diana Ravitch and Bill Gates object.
The problem with releasing teacher ratings is that, at least in ELA, the worst kind of teaching makes test scores increase. One teacher at my school, for example, only teaches test prep. Everything students read is a 1.5-2 page uplifting historical biography of a female or racial minority who invents something or explores somewhere and demonstrates incredible pluck and anachronistic open-mindedness. Every writing assignment is a short paragraph response to these biographies that restates the question and includes at least three supporting details. The kids, of course, hate the class and are learning to hate reading and writing. But I'm sure this guy's rating will be high. Other teachers in my school teach novels and assign research essays and writing poetry as homework; one of the very best (I observed his class when student teaching so I know first-hand that he's amazing) has a rating in the lowest quarter.
I am willing to believe the math ratings are meaningful (at least in the last few years, after they moved the tests from January to April), but the ELA ones are a complete joke. If I had a child in the system, I would look for a teacher with a very low "effectiveness."
Personal note: I taught English for only one year, 4 years ago, so my test-teaching rating exists but will not be released. I am told that in a few years my chess teaching be evaluated using a similar 60% classroom observation / 40% value added model, with ratings instead of test scores used to determine what "value" I am "adding" to my students. This is welcome news, since ratings are a legitimate assessment tool.
I would add that I'm not super liberal about education: I am absolutely against tenure and think firing bad teachers should be much easier. I think measuring teacher effectiveness is extremely important. I loved standardized tests as a student and did very well on them. But the state ELA tests are not good assessments and the grading of the subjective portions of them is ridiculous: inconsistent, unreviewable, unappealable and completely opaque.