Interest in school-based strategies to support student social and emotional learning (SEL) is strong. Although SEL policies and programs designed to support the development of student competencies have advanced significantly, less work has been done to develop methods of assessing student social and emotional competence. This article briefly reviews developments in the field of social and emotional competence assessment and examines challenges and opportunities in their applied use, including (a) balancing the priorities of assessment developers and educators; (b) ensuring that the inferences and decisions made from SEL assessment scores are supported by evidence of the assessment's psychometric merit; (c) establishing conditions for SEL assessment and data use that maximize benefit while mitigating risks; (d) coordinating standards, assessment, programs, and professional learning; and (e) balancing highly focused assessments that by design do not vary in content or format, and the varied cultural contexts in which they may be used.