摘要：I would like to offer a different take on the policy issues related to value-added estimates than that provided in Jesse Rothstein’s article. I believe that the primary value of these estimates is in illustrating how much difference there is between teachers. When the estimates are made in low-stakes situations where there is little incentive to teach to the test, estimates of the variance in teacher quality are very precise. In this article, I discuss the implications of the results of these types of studies, and then explore the implications for teacher policy. I believe that where Rothstein’s argument falters is that there are not currently any school systems that make teacher personnel decisions solely on the basis of value-added estimates, nor am I aware of any current proposals for such a system. For example, in regard to the District of Columbia policy described by Raj Chetty, only 18 percent of teachers in the system have value-added scores available, so this information is clearly only a relatively small part of what goes into making firing and bonus decisions
