It is established that the socio-economic status (SES) of individual students is strongly associated with academic achievement but less is known about this relationship when both student and school socio-economic status are considered. To examine these associations at a finer grain, with the intent of informing educational funding policy, we subjected Australia's 2003 PISA data set to secondary analysis to better understand the reading and mathematics achievement of students with varying SES, across a range of school SES groupings. Our descriptive analyses show that increases in school SES are consistently associated with increases in students' academic performance, and that this relationship holds regardless of individual students' SES. In Australia, the socio-economic profile of the school matters substantially in terms of academic achievement. We discuss the implications of these findings in the context of the current discussion around federal school funding policies, with particular attention given to the association of school composition with student achievement. (Contains 2 tables and 2 figures.)