KidzMath is an after-school math enrichment program that uses cooperative games and storybook-based activities to promote mathematical understanding and social development. AfterSchool KidzMath is designed to support children’s mathematical skills, confidence in mathematical abilities, increased enjoyment of mathematics, and children’s ability to work with others. Sacramento START (Students Today Achieving Results for Tomorrow), an after-school program whose aim is to help children throughout the Sacramento region succeed both academically and socially, implemented AfterSchool Kidzmath over the span of two years (2005-2007). The program was implemented in 23 Sacramento START sites situated in the Sacramento City Unified School District. Implementation followed a commitment from Sacramento START to use the program a minimum of twice a week for 30-40 minutes. START provided data for students who participated in KidzMath. Data were provided for the study years (2005-2007) and, to provide a baseline, for years 2002-2005. Data were provided by the Sacramento City Unified School District for additional children who served as controls. With information on which students participated in KidzMath, student demographics data, and California Standards Test Math scores, a longitudinal analysis was conducted to determine if student test scores benefitted from participation in KidzMath. The analysis found that, after controlling for factors such as gender, grade level, ethnicity, language fluency, the percentage of students at a school receiving free/reduced lunch, base Average Performance Index (API) of the school, and average parent education level of the school, that students who participate in KidzMath are associated with higher test scores. Students who’ve been in the program and exit continue to grow at higher rates than students who did not participate in the program, but this effect diminishes over time.