Differentiated instruction (DI) is an educational praxis that is built on the premise that all students can be engaged in learning and achieve positive academic outcomes. Previous research in secondary schools has shown promise in the success of DI practices and outlines the importance of sustained professional development (PD) for teachers. There is, however, little research on DI within senior-secondary classrooms in the Australian context. This research is part of a larger study which recruited 12 participants from three schools across two states in Australia, and aimed to investigate teachers' perceptions of school leadership and support in implementing DI in their classrooms as well as awareness of relevant policies. Findings indicated that when teachers were aware of policies involving DI, they tended to describe policies relating to special education. This suggests that DI is viewed by these teachers as an approach for students with additional needs rather than seen as a whole class philosophy. Similarly, the results indicated that when teachers said that leadership supported them in using DI, this support was commonly reported as isolated professional development in supporting students with additional needs. Discrepancies around awareness of DI policies were also found between teachers at the same school, with those in leadership roles indicating that requirements to utilise DI were embedded in their general teaching and learning policy. Implications for future practice and policy are discussed.