Students' basic reading and math skills can decline significantly during the summer months. Most attribute this to the prolonged period during which young students are outside of a structured learning environment (Cooper et al 1996). While summer learning loss occurs among all income groups, the effects are more pronounced for those from lower-­-income households than those from higher-­-income households where families have sufficient resources to provide enriching summer activities including camps, lessons, tutoring, art programs, and such (Entwisle, Alexander, and Olson 1997). These losses begin even in the earliest years of K-12 schooling and accumulate from year to year as students move through the crucial years of learning to read and have lasting impacts on student achievement (Alexander et al 2007). Moderate levels of evidence suggest that summer programs provided as school can ameliorate regression in achievement over the summer holidays (e.g. Borman and Dowling 2006). These findings have led to renewed interest in summer programs designed to mitigate, or even reverse, the trend of summer learning loss. This paper shares additional findings on the effect of the program through the first grade year. The results show that across four outcome domains of interest--Expressive Vocabulary, Letter-Word ID, Applied Problems, and Basic Writing--students randomly assigned to spend the summer in K-3 Plus outperformed those who were randomly assigned to receive regular school year services only. Results, while preliminary, suggest that the K-3 Plus model is an effective way to improve student achievement in high-poverty schools by ameliorating summer learning loss. A table is appended.