This paper summarizes investigations of school connectedness completed by the Social Development Research Group in two longitudinal studies, the Seattle Social Development Project and Raising Healthy Children. The theoretical importance of school connectedness, empirical support for the theoretical propositions of the impact of school connectedness on a variety of problem and positive behaviors, and the impact of interventions to improve school connectedness as a "mechanism to improve outcomes" for children and adolescents are described. This paper uses a definition of school connectedness and school bonding, derived from control theory and revised by investigations of the concept. The term used for school connectedness, school bonding, consists of two primary and interdependent components: (1) attachment, characterized by close affective relationships with those at school; and (2) commitment, characterized by an investment in school and doing well in school. Results of these studies provide evidence of the importance of school bonding for promoting academic success, reducing barriers to learning, reducing health and safety problems, and reducing deliquency, violence, gang involvement, drug use, and dropout. (Contains 1 table.)