This article presents emergent findings about the effective use of data for informing teaching and learning at the system, school, class and learner levels. It draws on policy frameworks, inquiry processes and resources trialled in the Department of Education and Children's Services (DECS) in South Australia. DECS has used a range of learner achievement and multiple measures in order to understand what makes a difference in our preschools, schools and regions. From this evidence DECS is developing teacher-friendly information systems and professional learning resources as a way to help teachers and the leaders of schools and preschools to analyse and present data effectively, and use it to drive improvement.