In an unexpected action last summer, the Los Angeles Times published the ratings of teacher effectiveness for 6,000 teachers by name. This is a potential game-changer. The publication created a firestorm. The unions were apoplectic. A vocal set of commentators attacked this action from a variety of viewpoints. Nonetheless, it shows signs of spreading – to New York City and elsewhere. Since my research started this development, I believe it is useful to share my perspectives on how we should judge this development and whether we should stop its spread. What did the Times do? It hired a professional analyst to link student gains on state achievement tests to specific teachers. These estimates, generally called value-added scores, take into account what students knew upon entry into the classroom along with other characteristics of the students and assess statistically how much the average student learned during a year. The Times then identified each teacher and published the results so that everybody, including importantly parents, could learn how effective each teacher was at raising the measured achievement of students. What are the advantages and disadvantages of this? This approach, the focus of considerable scholarly research, correctly attempts to isolate the impact of the teacher from other factors that affect achievement – families, peers, neighborhoods, and the like. Thus, it is designed to make judgments of what the teacher contributes as opposed to the specific draw of students in the classroom. Moreover, it provides an objective measure of teacher performance. That is not to say, however, that it is without problems. First, it depends on the areas that are tested – typically, math and reading but not science, social studies or history. Second, the statistical measures typically include various errors in assessing teacher performance because the tests themselves are inaccurate assessments of knowledge. Thus, the rankings from the value-added measures may be imprecise. What are the opposing arguments? Those favoring release of this information have a simple position: Parents have a right to know the effectiveness of their child’s teacher, and policymakers should take performance into account. Those opposing this argue the problems: It is a narrow and imperfect measure of teacher effectiveness and thus should not be released because parents and others will place too much weight on it. The teachers unions in particular do not want to enter into a discussion of which teachers are not performing well, because they have generally committed to defending all teachers and such information makes their defense difficult. As somebody deeply involved in the underlying science behind these measures, I see valid arguments on both sides. That having been said, there has been little movement toward a more thorough evaluation system that incorporates broader measurement of teacher effectiveness. The union position is to argue that we need to develop reliable and accurate evaluation systems – but then to block any use of evaluation systems that focus on classroom performance. One needs only look to Washington, D.C., to see this. Michelle Rhee worked to develop a thoughtful and elaborate evaluation system based on classroom observations and supervisor ratings along with incorporating value-added measures of performance where possible. This proposed evaluation system could support both large bonuses to exceptional teachers and elimination of teachers who showed that they were ineffective. The unions resisted these efforts, forcing her to institute a series of unilateral personnel actions against the most ineffective teachers. Now Rhee is gone from D.C., providing direct evidence of the difficulty that follows any attempt to evaluate performance. I personally would not like to see personnel decisions made solely on the basis of value-added scores. But typical evaluations today are useless, because only a minuscule number of teachers are rated anything but great and because these ratings are never used in making personnel decisions. Thus, while I would like to see a broader evaluation program, the introduction of a value-added system puts information on effectiveness into play. The importance of improving our schools is too great simply to dismiss such information as imperfect. The current system of evaluations is completely broken. And, there is virtually no chance of improving schools without paying attention to which teachers are effective and which are ineffective.