This randomized controlled trial evaluated the efficacy of the Using Data program in improving teacher practices and student achievement in mathematics. Sixty schools were randomly assigned to treatment and control conditions. The study found that after one year, teachers in the treatment schools reported more frequent data use, greater data literacy, and more positive attitudes towards using data compared to the control teachers. For students, no overall effect was found after two years. However, students of teachers in the lowest performing schools at baseline who received the intervention showed moderate improvements in mathematics achievement. The study provides preliminary evidence that the Using Data program can improve teacher practices and student outcomes in high-needs schools.