Through school-based networks, parents obtain information, practical help, and other resources. Because networks vary by size and structure, access to these resources is uneven. What accounts for differences in access to social ties and in the mobilization of those ties to provide resources? In this article, we analyze a network of mothers of eighth graders at a Philadelphia public school. With a near-complete census of network ties, we explore mothers' access to and mobilization of information and practical help through social ties. We find that mothers' school-based participation, rather than their race or class-based social position, is associated with resource access and mobilization. Importantly, greater levels of participation increase the likelihood that a mother will "provide"--but not "obtain"--information and practical help. Our results can help inform public policy and practice on family and community engagement in schools.