In this webinar, the High Tech High Graduate School of Education research team presents its findings from a field-leading 2-year study in which teachers engaged in collaborative inquiry to test, refine, and spread student-centered approaches in mathematics. The teachers' main goal is to develop instructional strategies in k-12 classrooms that help students experience a sense of belonging, develop their mathematical agency and identities, and enrich their understanding of mathematics. Presenters discuss how they centered equity and students in instructional decision-making using "lesson study" and showcase positive trends in student achievement, agency, and belonging, especially for Black and Latino/a students.