The purpose of this study was to examine the efficacy of IXL Math in an elementary school context, using a randomized-control trial (RCT). This study examined mathematics achievement trajectories of 545 Grades 3-5 students across four elementary schools in a small Michigan school district during the 2022-23 school year. Teachers were randomly selected to use IXL Math (treatment condition) or business-as-usual instruction (control condition) for the winter and spring of the 2022-23 school year. Outcome variables included spring 2023 Renaissance Star mathematics scores (progress monitoring) and spring 2023 M-STEP mathematics scores (state test scores). Prior achievement variables included winter 2023 Renaissance Star mathematics scores and spring 2022 M-STEP mathematics scores. Treatment teachers were also administered a survey focusing on teacher experiences with and reactions to the IXL Math program. District-wide, nine of 11 treatment teachers volunteered to complete the survey. Hierarchical linear modeling (HLM) with students nested within teachers was used to complete the main impact analyses, while quantitative survey data were analyzed descriptively, and open-ended items were analyzed qualitatively. The results of the main impact analyses showed a significant positive impact of IXL Math on student mathematics achievement, with treatment students gaining approximately 10-points more on the Renaissance Star mathematics assessment than did control students. The effect size of this impact was 0.13 SDs, indicating a small-to-moderate practical impact of IXL Math on student mathematics achievement. Subgroup analyses showed that IXL Math had additional significant positive impacts on Hispanic, special education, ELL, and free and reduced meal (FARMS) students, with the magnitudes of these impacts ranging from 13-17 points. In addition, teacher perceptions of IXL Math were generally very positive, especially in relation to professional development and overall program perceptions. In all, the results of this study provide evidence supporting efficacy of IXL Math in improving student mathematics achievement, especially for student subgroups that historically had started at lower performance levels.