Applying qualitative comparative analysis (QCA), this study explores the configurations of conditions that contribute to the polarisation of high-performing and low-performing secondary schools in Victoria, Australia. It is argued that the success and failure of schools can be understood in terms of causal complexity, where one or several configurations of conditions can cause a given outcome. The study identifies that there is no single condition alone that produces high or low performance. However, the study does reveal the existence of multiple configurations or causal relations that tend to produce school success or school failure. Relative to the dataset considered in this study, three configurations related to success and almost twice that many configurations underpinning failure are identified. The polarisation of the high-performing and low-performing schools and persistent inequality are complex phenomena. This study presents QCA as a useful and alternative methodology for researchers to uncover such complex phenomena over and above large-scale quantitative and classical analysis.