Of all the social science theories that have been applied to school desegregation policy, none has a longer or more important history than the harm and benefit thesis. In its simplest form, the thesis holds that school segregation is harmful to the social, psychological, and educational development of children, both minority and white, and that school desegregation is beneficial for undoing or at least ameliorating the damages from segregation and discrimination. While the harm and benefit thesis began as a purely social science theory, its apparent endorsement by the Supreme Court in Brown gave the thesis an enormous boost, elevating it from academic theory to moral authority. From Brown to the present time, the harm and benefit thesis has played a curious and bifurcated role in the evolution of school desegregation policy. Although it began as a social science theory that had apparently found its way into judicial doctrine, its role in the courts soon parted from its role among educators, social scientists, and civil rights groups. On the judicial front, a number of lower court decisions in the early 1970s stressed the harms of school segregation and the benefits of integration remedies. The Supreme Court itself never again explicitly addressed the harm and benefit thesis after Brown, however, and its judicial relevance diminished over the next three decades as the high Court majority restricted the application of Brown to government-enforced school segregation. For this reason many constitutional scholars have long maintained that the psychological harm finding in Brown is not an essential part of constitutional law. To the extent that a harm thesis can be inferred from current judicial doctrine, then, harm arises only if school (or other) segregation is sanctioned by law or official action. For many other actors on the desegregation stage, however, the harm and benefit thesis has had a far broader applicability. During the periods when the earliest formulations began to appear, such as that by Gunnar Myrdal in 1944 or the famous doll studies of Kenneth and Mamie Clark in the late 1930s, most existing segregation was in fact sanctioned by law, and thus most social science research on this issue of necessity reflected the effects of official segregation.