The National Research Council's (NRC) statement and description of features of settings that have value for positive youth development have been of great importance in shifting discourse toward creating programs that capitalize on youth motivations toward competence and connections with others. This assets-based approach to promote development is consistent with the Classroom Assessment Scoring System (CLASS) framework for measuring and improving the quality of teacher-student interactions in classroom settings. This chapter highlights the similarities between the CLASS and NRC systems and describes the CLASS as a tool for standardized measurement and improvement of classrooms and their effects on children. It argues that the next important steps to be taken in extending the CLASS and NRC frameworks involve reengineering assessments of teacher and classroom quality and professional development around observations of teachers' performance. This might include using observations in policies regarding teacher quality or a highly effective teacher that may emanate from the reauthorization of No Child Left Behind and moving away from a course or workshop mode of professional development to one that ties supports directly to teachers' practices in classroom settings. (Contains 1 figure and 23 notes.)