In this article, we aimed to contribute to a fuller understanding of the complex social ecologies that shape students' academic development by focusing on richer and more precise conceptualizations of mesosystem effects. First, building on bioecological models, we argued for the importance of "collective influences," defined as influences from multiple microsystems that act in concert to shape students' academic functioning and development. We identified three ways collective effects can operate: (1) coactively, (2) contingently, and (3) sequentially. Second, we demonstrated the utility of this framework by using it to organize a narrative review of 32 studies of the effects of parents, teachers, and peers on students' academic engagement. The framework was used to classify studies, integrate findings, identify trends, and suggest directions for future study. Third, we explored next steps in the conceptualization and study of complex social ecologies, by incorporating perspectives that are more developmental, cultural, sociohistorical, and inclusive.