Achievement grouping has been practised in a number of forms and contexts for over a century, and has been the subject of copious amounts of research. Despite a general consensus in the research that between-class achievement grouping provides no overall benefit for students, the practice has persisted in various guises. One form is that which occurs for individual subject areas. This is quite common in high schools, particularly for mathematics, and is also practised in a number of primary schools in New South Wales and overseas. Recent research in this field involving primary school students and teachers has investigated the affective outcomes of such practices, but academic outcomes at the primary level have not been studied in recent decades. This paper examines the academic outcomes of between-class achievement grouping in primary literacy and numeracy classes. Results from Basic Skills tests are compared between two groups of schools – one which regroups students for these areas, and one where students remain in a mixed achievement class for all subjects. The conclusion reached is that the current regrouping practice provides no academic advantage for students.