A randomized controlled trial group design study funded by IES NCR Grant R305A090527 was conducted in which 16,307 3rd, 4th, and 5th grade students in 52 school grade-level clusters were randomly assigned to receive ST Math (program revision Gen3), a supplemental mathematics software instructional intervention, or to a business-as-usual mathematics instruction control. After checking for acceptable attrition, and with control for baseline equivalency, Intent-to-treat (ITT) hierarchical linear model (HLM) findings on the California Standards Test math reveal a significant difference in differences treatment effect at the student level across all grades (p<0.0005). Analysis of the individual grade-levels reveals larger increases in student standardized math scores in schools receiving the intervention than controls, with ANCOVA revealing significantly higher increases achieved individually for 4th and 5th grades (p<0.001). [This report was published by the MIND Research Institute.]