This report draws on insight from a nationally representative survey of schools in England, a convenience sample of nearly 1,500 supply teachers and qualitative research with 60 supply teachers, 22 leaders, and seven supply teacher providers conducted in 2023. It explores individuals' motivations for entering the supply market, along with the reasons schools use supply teachers and the ways in which they are deployed. Current models for the procurement, management and professional development of supply teachers are also examined.