The purpose of this mixed-methods study was to test the efficacy of nine Characteristics that previous research has suggested help account for the contribution that districts make to their students’ success and, in particular, to closing achievement gaps among those students (Leithwood, 2010; 2011; Leithwood & Azah, 2017; Leithwood & McCullough, 2017). The study also aimed to deepen understanding about the features of each district Characteristic in its most effective state. In addition, the study assessed the extent to which a selected set of school, classroom and family Conditions significantly mediate district effects on students’ cognitive and socio-emotional capacities. Data collected by the study provided answers to seven more specific questions as a means of accomplishing the overall objectives for the study.