Prior research suggests that summer learning loss among low-income children contributes to income-based gaps in achievement and educational attainment. We present results from a randomized experiment of a summer mathematics program conducted in a large, high-poverty urban public school district. Children in the third to ninth grade (N = 263) were randomly assigned to an offer of an online summer mathematics program, the same program plus a free laptop computer, or the control group. Being randomly assigned to the program plus laptop condition caused children to experience significantly higher reported levels of summer home mathematics engagement relative to their peers in the control group. Treatment and control children performed similarly on distal measures of academic achievement. We discuss implications for future research.