This study explores the extent to which differences in research design explain variation in Head Start program impacts. We employ meta-analytic techniques to predict effect sizes for cognitive and achievement outcomes as a function of the type and rigor of research design, quality and type of outcome measure, activity level of control group, and…

This paper provides practical guidance for researchers who are designing and analyzing studies that randomize schools--which comprise three levels of clustering (students in classrooms in schools)--to measure intervention effects on student academic outcomes when information on the middle level (classrooms) is missing. This situation arises…

This article presents evidence from a national evaluation of the effects of 21st Century Community Learning Center after-school programs. The study was conducted in 12 school districts and 26 after-school centers, at which 2,308 elementary school students who were interested in attending a center were randomly assigned either to the treatment or…