U.S. public school students have lost out on considerable mathematics learning since the beginning of the coronavirus disease 2019 (COVID-19) pandemic in 2020. Public schools can take many steps to improve mathematics achievement, but to help students who are most at risk, those steps will need to keep equity front and center by focusing particularly on mathematics learning recovery for students who are Black, Hispanic, or experiencing poverty--students whose performance fell precipitously over the past few years. In this RAND Perspective, authors lay out a research agenda for the American Mathematics Educator Study by synthesizing what they know from mathematics education research regarding key factors that shape equitable, high-quality mathematics teaching and learning. Those factors include math learning opportunities for students, including access to rigorous math courses and interventions, along with resources for teachers, such as high-quality instructional materials, curriculum-aligned professional learning, and support for meeting students' diverse math learning needs. Authors also provide near-term recommendations for mathematics education policy and practice.