The purpose of this study was to examine the relationship between students' engagement with Legends of Learning's Math Basecamp (MBC) and students' math achievement at the elementary school level in Rialto Unified School District (RUSD) in California. Researchers examined the association between MBC usage and student achievement scores on the Smarter Balanced Mathematics assessment for 3,273 students in grades 3-5 using ordinary least squares (OLS) regression. Additionally, researchers used propensity score matching to determine a causal relationship between MBC usage and math scores for 1,608 students. OLS regression results reveal that as the number of sessions of Legends of Learning's Math Basecamp increases, achievement on California's Smarter Balanced Mathematics assessment increases significantly. Further, propensity score matching results indicate that completing at least 24 sessions of MBC significantly increases student scores on the Smarter Balanced Mathematics assessment. Further research is needed to confirm a causal relationship between participation in Math Basecamp and math achievement, which could be done in a Randomized Controlled Trial (RCT) or a robust quasi-experimental design (QED). Expanding future studies to include additional populations and settings, as well as additional analytic approaches can confirm the robustness of these findings and the generalizability of Math Basecamp's impact. [This report was prepared for Legends of Learning.]