School attachment is a robust predictor of adjustment in children and youth. Previous research has demonstrated effects of school context on student attachment, but individual-level contributions have not been explored. Our study examined the role of affiliative orientation in school attachment and aggressive behavior in children and youth from Grades 3 through 12. A total of 834 students in three school districts completed self-report measures of affiliative motivation, attachment to school, and frequency of physically and relationally aggressive acts. Results supported the hypothesis that students high in affiliative orientation reported higher levels of school attachment and lower levels of physical and relational aggression. Path analysis indicated that the relation of affiliative orientation to aggression was mediated by school attachment, but that the mediational effect was moderated by sex. Male students, and students of both sexes with low affiliative motivation, may receive special benefit from practices designed to increase school attachment.Social control theory, the dominant theoretical context in which school attachment has been explored, holds that attachment arises when students are rewarded for positive involvement in school (Hirschi, 1969). Ample research, both basic and applied, has provided evidence for the association of perceived rewards for positive involvement with school attachment. Interventions designed to increase school attachment and based on this model, for example, focus on increasing opportunities for positive involvement, developing the skills needed to take advantage of opportunities for involvement, and consistently rewarding involvement when it occurs. Classroom-level practices such as interactive teaching methods, small-group work, and regular reinforcement of positive involvement through teacher warmth and support have been shown to result in increased school attachment over time (Gottfredson, 1988;Hawkins et al., 1988). Similarly, school-level changes such as increased opportunity to participate in extracurricular activities and greater community support of schools also have resulted in higher levels of school attachment (Gottfredson, 1988). The social development model, a developmental elaboration of Hirschi's social control theory, proposes that individual-level differences also should affect the perceived rewardingness of involvement and thus school attachment (Catalano & Hawkins, 1996). The individual differences specified in the model are limited to cognitive ability and physiological arousal level; however, other theoretical models provide a rationale for considering personality factors that also might play a role in the perception of satisfaction and reward in a school context.In contrast to the social control model, Eccles and colleagues (1993) approached school attachment from a motivational perspective, considering it a function of the match between students' need for relatedness and autonomy and the degree to which schools meet those needs, or the "stage-environme...