A number of trends are converging to drive the need for more informed teacher data use. These include advocacy for formative assessment and the need for teachers to account for student learning. In this context, assessment literacy and data literacy have emerged as a focus in research and professional development. Problematically, research signals that developing assessment/data literacy is challenging with evidence that teachers may not have mastered relevant aspects of mathematics and statistics. This paper reports lecturer, student teacher and school leader views of the role and requirements of data literacy using data from a larger study into how to foster student teacher mathematical thinking for the breadth of teacher professional work. Data were generated via interviews, surveys and document analysis. Findings suggest a concern and opportunity to develop assessment/data literacy as this calls on mathematical and statistical understanding.