Dosage effects on school readiness: evidence from a randomized classroom-based intervention

Variations in the dosage of social interventions and the effects of dosage on program outcomes remain understudied. This study examines the dosage effects of the Chicago School Readiness Project, a randomized, multifaceted classroom-based intervention conducted in Head Start settings. Using a principal score matching method to address the issue of selection bias, the study finds that high-dosage levels of teacher training and mental health consultant class visits have larger effects on children's school readiness than the effects estimated through intention-to-treat (ITT) analyses. Low-dosage levels of treatment are found to have effects that are smaller than those estimated in ITT analyses or to have no statistically significant program effects. Moreover, individual mental health consultation services provided to high-risk children are found to have statistically significant effects on their school readiness. The study discusses the implications of these findings for research and policy.