The Wallace Foundation is funding a multiyear study in five urban school districts to determine whether voluntary summer learning programs are effective and what factors are associated with success. These districts have been pioneers in offering full-day voluntary programs for five to six weeks free of charge to large numbers of low-income elementary students, not just to those facing grade retention. Although the districts take different approaches to their programs, they all provide at least three hours of academic instruction per day by certified teachers, along with a range of enrichment activities such as art, music, tennis, and swimming. This brief summarizes the outcomes of two summers of programming (2013 and 2014) on 3,192 students accepted into the programs who had completed third grade before the first summer. Future research will analyze whether program effects persist after the students complete seventh grade. (author abstract)