The purpose of this study is to evaluate, using a randomized experimental design, the efficacy of TERC's "Using Data" program to change teacher behavior and improve student learning outcomes. The "Using Data" intervention provides professional development and technical assistance to teachers to help them use data collaboratively to identify and solve systemic student learning problems. The intervention was implemented by school-based data teams composed of a designated data coach and four grade 4 and 5 math teachers in Duval County Public Schools, a large, urban school district serving Jacksonville, Florida, during school years 2011-12 and 2012-13. In the first year of the study, teachers in the treatment group participated in professional development events and technical assistance sessions that exposed them to "Using Data" and helped them implement its processes. In the second year the teachers received additional assistance with implementation. Sixty (60) schools were recruited to participate in the study. The authors conclude that the weight of the evidence presented in this report indicates that "Using Data" improves teachers' outcomes after one year, and improves the outcomes of their students in high-needs schools after two years. Three appendices are included: (1) Study Questionnaires--Sample Questions; (2) Psychometric Analysis of "Using Data" Scales; and (3) Power Analysis.