The phrase “free, compulsory, and secular” is central to Australia’s understanding of its own education system. Yet the extent to which education in Australia, or anywhere else for that matter, can be described as “secular” is never clear or settled. This work examines the history of education in Australia, from 1910 through to the present, through an interdisciplinary survey of key scholarship and a series of six original case studies. It seeks to uncover the extent to which the education system has undergone a process of secularisation and argues that the very meaning of the term “secular” is always contingent and changeable.