This case describes a body of work structured around a research-practice partnership that began in 2013 to support the implementation and evaluation of a universal social– emotional learning curriculum in the Bellevue (Washington) School District. Research activities are organized around a Design-Based Implementation Research framework, which focuses on evaluating while also engineering the implementation of programs by collecting and using data. Design-Based Implementation Research is suited to refining and testing innovative strategies to enhance teaching and learning within school and agency contexts and is an extension of classroom-based design research that emphasizes collaborative and sustained engagement to enhance systematic inquiry and quality improvement. The partnership between Bellevue School District and the University of Washington 3-Dimensional Learning (3DL) Partnership focuses on a district-wide implementation and evaluation of RULER, an evidence-based social–emotional learning program. RULER focuses on helping teachers and children recognize, understand, label, express, and regulate emotions in the classroom with the goal of increasing student attentiveness, lessening conduct problems, and improving academic outcomes.