Background/Context: Schools are spending more money than ever on a growing number of educational technology programs which are designed to boost student learning outcomes, especially after the integration of online learning that was necessitated by COVID-19 pandemic school closures and disruptions (Instructure, 2024; Teras et al., 2020). Rigorous research, and particularly ESSA Tier 1 evidence, of the efficacy of these programs lags behind the speed of their development and adoption. Thus, it is important to continue to develop evidence about these programs in order to aid district leaders in their decision making about program adoption. Purpose/RQ: The purpose of this study was to use a rigorous research design to assess the impact of IXL's online learning platform on Grades 3-5 students' mathematics achievement. This study builds off prior internal evaluation studies of IXL Math which used quasi-experimental methods (e.g., Schonberg, 2021). Impacts across grade levels and subgroups were examined, and associations between IXL usage metrics and achievement gains were also analyzed. In addition, teacher perceptions of the IXL Math platform were examined regarding perceived student benefits, student engagement, implementation, strengths and weakness, and recommendations for improvement. Setting: The study took place across four elementary schools in Holland (MI) Public Schools (HPS). HPS is a small district that serves slightly less than 3,000 students. Demographically, nearly 70% of district students are White, followed by Hispanic/Latino (22%) and Black (5%) students. Participants: In these four schools, teachers and students in grades 3-5 participated in the study. Teachers were randomly assigned to either the treatment group (to implement IXL Math) or to the control group (to continue with business-as-usual instruction in their classrooms), with assignment balanced across grade levels. Eleven teachers (and the students in their classrooms) were assigned to implement IXL Math, and ten teachers were assigned to business-as-usual instruction. Student-level samples sizes were 263 students in the treatment condition and 282 students in the control condition. Treatment and control students were similar on demographic variables and no baseline differences were statistically significant. Additionally, both groups exhibited baseline equivalence on the pre-test (winter Renaissance Star mathematics), with an effect size difference of 0.09 SD between groups. Description of Intervention: IXL Math is a personalized comprehensive mathematics program that addresses nearly 1,500 math skills in Grades 3-5. Unlimited interactive questions are provided via real-world scenarios with built-in support and motivating rewards. Real-time diagnostic data on students' knowledge levels allow teachers to make data-driven instructional decisions and assign customized learning instruction and intervention. Research Design: Using a cluster randomized-control trial (RCT) design, Grades 3-5 HPS teachers were randomly assigned in January 2023 to either implement IXL Math or continue business-as-usual instruction. Teachers received access to IXL Math and began implementing in February and continued through the Spring semester. The impact of IXL Math on mathematics achievement was assessed in Spring 2023 on the Renaissance Star and Michigan Student Test of Educational Progress (M-STEP) mathematics assessments. In addition, IXL Math digital student-level usage data were collected, specifically to examine their associations with mathematics achievement score gains. A survey was also administered to teachers assigned to implement IXL Math to obtain perceptions of the IXL Math online platform. Data Collection/Analysis: Mathematics achievement and demographic data were obtained directly from HPS, while IXL Math digital usage data were obtained directly from IXL Learning. The teacher survey was administered online using the Qualtrics survey platform. Survey data were downloaded in July 2023, after the survey was closed. The impact of IXL Math was assessed on Renaissance Star and M-STEP math outcomes using Hierarchical Linear Modeling (HLM) with students nested within classrooms. Winter 2023 Renaissance Star Math scores were used as the prior (pre-intervention) achievement variable. Student-level demographic variables (student race/ethnicity, gender, IEP status, ELL status, and FRL status) were also included as covariates in all impact analyses. Because classrooms were randomly assigned within schools, we also added dummy variables for each school and grade, in accordance with WWC (2022) standards. Associations between IXL Math digital usage variables and student achievement gains were analyzed using the same models, replacing the treatment dummy variable with various usage variables. Stata v. 17.0 was used to conduct all analyses. Findings/Results: The main impact analyses (see Table 1) showed a significant positive impact of IXL Math on student mathematics achievement for Grades 3-5 students in HPS, with treatment students making approximately 10-point larger gains on the Renaissance Star Math assessment than comparison students. The effect size of this impact was 0.13 SDs, indicating a small to moderate practical impact of IXL Math. Additional subgroup analyses (see Table 2) showed positive impacts of IXL Math on Hispanic, special education, ELL, and free and reduced meal (FARMS) students, with magnitudes of these impacts ranging between 13 and 17 points. In addition, IXL Math usage metrics were significantly positively related with mathematics achievement measures, with correlations ranging between 0.30 to 0.57 in magnitude (see Table 3). Survey results from IXL Math teachers were generally positive, especially in relation to professional development and overall program perceptions. Conclusions: The results of this study showed evidence supporting the efficacy of IXL Math in relation to student mathematics achievement. Additionally, positive teacher perceptions of the IXL Math platform indicate the social validity of this program. One limitation of this study is the unique setting of this study: Grades 3-5 teachers and students in one small school district. Thus, the results of this evaluation may not generalize to other contexts or student populations and further study is needed to confirm whether these results would replicate in other settings.