This special issue highlights recent research on measures of early adolescents' development and the school contexts in which they spend their time. We are particularly interested in measures with direct application--providing actionable data to teachers, principals, parents, school counselors, or the students themselves, in ways that promote social-emotional and academic learning. In this introduction, we highlight the ways in which articles in this special issue offer rigorous, relevant, and feasible approaches to this measurement work and discuss future directions for research and practice in this area.