The goal of this proposed research is to identify the mechanisms by which structural characteristics and proximal processes in classrooms exert influence on adolescents? academic engagement and achievement in mathematics. An understanding of these mechanisms will provide a solid basis for educational interventions that can target both classroom resources and processes. Moreover, this study will examine different dimensions of classroom environment in relation to a host of valued educational outcomes?achievement, behavior, affect, and cognition at the student level. Knowledge of which aspects of classroom structures and processes relate to positive mathematics achievement will lay the foundation for future randomized field experiments to improve classroom quality and consequently impact valued educational outcomes.