Research has determined that low-income students lose ground to more affluent peers over the summer. Other research has shown that some summer learning programs can benefit students, but we know very little about whether large, district-run, voluntary programs can improve student outcomes among low-income students. To fill this gap, The Wallace Foundation launched the National Summer Learning Project in 2011. This six-year study offers the first-ever assessment of the effectiveness of large-scale, voluntary, district-run, summer learning programs serving low-income elementary students. The study, conducted by the RAND Corporation, uses a randomized controlled trial to assess the effects of district-run voluntary summer programs on academic achievement, social and emotional skills, and behavior over the near and long term. All students in the study were in the third grade as of spring 2013 and enrolled in a public school in one of five urban districts: Boston; Dallas; Duval County, Florida; Pittsburgh; or Rochester, New York. The study follows these students from third to seventh grade. Our primary focus is on academic outcomes, but we also examine students' social and emotional outcomes as well as behavior and attendance during the school year. We have also collected extensive data about the summer programs to help us examine how implementation is related to program effects. This document includes the technical appendixes that accompany the third report resulting from the study, Learning from Summer: Effects of Two Years of Voluntary Summer Learning Programs on Low-Income Urban Youth (Augustine et al., 2016). (author abstract)