This report considers the extent to which Australian secondary school teachers are teaching subjects other than those in which they have specialised. It provides new data on the extent of out-of-field teaching overall and in a selection of subject areas, based on further analysis of the 2013 Staff in Australia's Schools (SiAS) survey. In addition, the report uses new questions in the SiAS 2013 survey to assess the proportion of students affected by out-of-field teaching in selected subjects.