School food has a major influence on children's diet quality and has the potential to reduce diet inequalities and non-communicable disease risk. Funded by the UK Prevention Research Partnership (UKRI), we have established a UK school food system network. The overarching aim was to build a community to work towards a more health promoting food and nutrition system in UK schools. The network has brought together a team from a range of disciplines, while inclusion of non-academic users and other stakeholders, such as pupils and parents, has allowed the co-development of research priorities and questions. This network has used a combination of workshops, working groups and pump-priming projects to explore the school food system, as well as creating a systems map of the UK school food system, and conducting network analysis of the newly established network. Through understanding the current food system and building network expertise, we hope to advance research and policy around food in schools. Further funding has been achieved based on these findings, working in partnership with policy makers and schools, whilst a Nutrition Society Special Interest Group has been established to ensure maximum engagement and future sustainability of the network. This review will describe the key findings and progress to date based on the work of the network, as well as a summary of the current literature, identification of knowledge gaps and areas of debate, according to key elements of the school food system.