The out-of-field teaching phenomenon is a complex, multilayered thing that has been intertwined with the workforce planning and management of education systems globally for decades, and it is likely to stay part of education in the future. Out-of-field teaching is defined as teaching that falls outside a teacher’s field of qualification or expertise, whether in a specific subject or at a different year level. Teachers teach out of field for a variety of reasons, many of which are embedded in enduring workforce management challenges and the changing priorities of education systems that bear down on the constrained resources of individual school contexts.