Using computers to evaluate teachers based on student test scores is more difficult than it seems. Value-added modeling is a genuinely serious attempt to grapple with the difficulties. Value-added modeling carries the promise of measuring teacher quality automatically and objectively, and improving school systems at minimal cost. The essence of…

Drug studies are often cited as the best exemplars of evaluation design. However, many of these studies are seriously biased in favor of positive findings for the drugs evaluated, even to the point where dangerous effects are hidden. In spite of using randomized designs and double blinding, drug companies have found ways of producing the results…

This article considers potential impediments to the estimation of teacher quality caused primarily by the purposeful behavior of families, administrators, and teachers. The discussion highlights the benefits of accounting for student and school differences through a value-added modeling approach that incorporates a student's history of family,…

Single equation regression models have been used rather extensively to test the effectiveness of Supplemental Instruction (SI). This approach, however, fails to account for the possibility that SI attendance and the outcome of SI attendance are jointly determined endogenous variables. Moreover, the standard approach fails to account for the fact…