This paper examines how controlling statistically for baseline covariates (especially pretests) improves the precision of studies that randomize schools to measure the impacts of educational interventions on student achievement. Part I of the paper introduces the concepts, issues, and options involved. Parts II and III present empirical findings…

Several years ago, a coalition of Chicago civic groups met to determine the scope of the urban dropout problem and develop strategies for dealing with it. The resulting research program rejected both attrition and survey analysis approaches in favor of direct examination of all student records for three graduating classes (1982, 1983, and 1984)…