In education, there is a history of pitting philosophy against science. In mathematics, a similar divide exists between evidence-based practice and philosophy-based practice. Philosophy-based practices are very prevalent in math and are not simply benignly ineffective tactics. The science of math is a movement that focuses on using objective evidence about how students learn math in order to make educational decisions and to inform policy and practice. The authors believe that school psychologists, as data-based decision-making consultants and MTSS experts in schools, are critical allies in promoting research-based practices in mathematics. This article is the first of a series of articles appearing in "Communiqué" about how school psychologists can adopt and promote evidence-based practices in math assessment and instruction. Future articles will address topics including equity in mathematics, curriculum-based measurement updates in mathematics, math anxiety and timed tasks, how to build intensified individualized math interventions, and how to use math MTSS data for program evaluation and eligibility determination.