The purpose of this study was to introduce a motivational property of the group, friendship group engagement vs. disaffection, and to examine different composition models for combining individual reports into an indicator of a group-level property. Data were collected from 312 ninth grade students and their teachers. Self-reported friendship group (FG) engagement and disaffection were related to self-reported classroom engagement, aggression, and peer problem behavior, but not to teacher-reported classroom engagement. Group-reported FG engagement and disaffection were related to self-reported FG engagement and disaffection, classroom engagement, aggression, and peer problem behavior, but these relationships were moderated by within-group agreement on the group property. Findings underscore the importance of a priori conceptualization of group-level properties that are theoretically linked to adolescent adjustment, and the need to consider composition models when aggregating individual reports to create profiles of the group. Implications for future work on capturing properties of friendship groups are discussed. (Contains 1 figure and 4 tables.)