This chapter overviews theory and recent research on the role that group processes play in social exclusion and resource allocation decisions in childhood and adolescence. The Social Reasoning Development (SRD) model draws upon theory and research in both developmental psychology and social psychology. The model integrates and extends social domain theory and social identity development theory by considering together how children's reasoning and group identity are important to the group processes underlying social exclusion and resource allocation. Group processes are central to the development of social cognition and moral judgment. It reflects many different aspects of social development, including group identity, group affiliation, and interpretations of group goals. The SRD model emphasizes the impact of group norms on children's moral and social decision making and reasoning, and group norms have an important impact on children's resource allocation decisions.