This study aims to characterise inter-organisational collaboration and support networks between schools in a privatised, marketised, and competitive school system. It is located within and contributes to a body of literature on school networks, which has primarily focused on studying the architecture and conditions for the sustainability of the arrangements where collaboration and support between schools are meant to take place. However, there has been less focus on examining the partnerships themselves, particularly those formed organically by schools. This is an exploratory study that takes a novel convergent mixed-method egonet Social Network Analysis approach. Primary data were produced from interviews with sixteen primary school headteachers from a local area in Santiago, Chile. Participants were encouraged to name and reflect on other schools with which their schools have an inter-organisational relationship. Insights show that schools draw on both mandated and organically formed inter-organisational relationships to collaborate and support each other. These ties tend to be built with schools alike and geographically close. Some of the main drivers to turn to others are ensuring the sustainability of schools, generating coordinated responses to policy mandates, sharing practice and knowledge, and ensuring students’ schooling trajectories. This study, situated within the broader context of school networking literature, proposes that schools exist within multiple networks, with various connections serving different purposes, some of which are rarely acknowledged. It suggests that while formal school networks and governance structure are important, they are insufficient to represent the inter-organisational relationships in which schools are involved.