This study performed a rigorous empirical evaluation of the efficacy of IXL Math, a popular PreK-12 educational technology platform designed to supplement a conventional standards-aligned curriculum. In both propensity score matching (pre-processing) and multiple regression analysis, the study controlled for baseline performance, grade level, and key school and student characteristics. Results revealed statistically significant larger gains among IXL schools relative to comparable non-IXL schools over the course of a three-year intervention in grades 3-8. Thus, the study not only built upon the large body of extant evidence supporting the efficacy of IXL Math, but it also did so using methodology that meets the requirements for ESSA Tier 2 (moderate evidence) as well as WWC standards with reservations. Last but not least, this study provided a formal evaluation of the benefits of a three-year intervention. An independent review determined that the study meets the requirements for ESSA Tier 2 and WWC standards with reservations (see Mislevy, Seftor, & Wei, 2021). [This report was prepared by IXL Learning.]