In order to help social learning become a more operational theory, this thesis attempts to create a better understanding of the conditions conducive to effective group action in a social context. Parts one and two trace the evolution of social learning theory in education and planning. Part three attempts to identify within a practical setting -- a ten-week project to plan and develop an ecology site with eighth graders -- elements of this dual process of individual change through experience and social system change through experimentation. Part four examines the impact of group structure (size and composition) on group effectiveness in participatory planning and action. It was found that four students to one facilitator appeared to be the most consistently effective ratio for beginning groups and that heterogeneity in group composition appeared to lower group effectiveness. Other variables considered included the nature of the task activity, the role of the facilitator, time, the role of structure, expert knowledge, and consensus on goals in supporting participatory action. In part five, implications for research and action are drawn from the experience with the junior high students. (Author/MLF)