This research project investigated adolescent group activity in a high school. Using participant observation, the researcher joined small, informal student groups to be able to describe and explain inschool activities and their relations to other features of the school environment. During five months of daily interaction with the students, the researcher participated in three groups that reflected these similar characteristics: (1) all were active social units with the members spending most of the day in one another's company; (2) distinct group activities took place when opportunities arose to interact; (3) group activities had little to do with the academic sector of the school; (4) group membership did not interfere with a particular member's academic achievement; (5) little cross-communication occurred between groups; and (6) all groups showed concern for and complied at least minimally with school regulations. These findings are explained as a pattern of behavior in response to the school environment. (Author/MLF)