Assessment for learning places greater emphasis on assessment being linked intrinsically to the teaching and learning process. In this context summative and formative assessment become critical in providing feedback to teachers and students about what is understood and where learning and subsequently teaching should be directed to enhance student understanding. In NSW, this focus has required a major shift in teacher thinking and practice. A study using the Structure of the Observed Learning Outcome (SOLO) model as a theoretical framework was developed to provide thirteen secondary mathematics and science teachers with a structure and language to reconsider their assessment and teaching practices for Years 7-10. This paper describes the mid-project findings after teacher involvement in a two-year professional development program. Science teachers recognised the usefulness of the SOLO model for planning a range of assessment tasks that explored students' scientific understandings and then implemented this knowledge to restructure their science programs. Alternatively, mathematics teachers applied the model to identify developmental pathways in mathematical conceptual understanding as a means of improving their teaching strategies in the classroom. These results demonstrated a major shift in teachers' views of assessment and their practices from initial interviews conducted at the outset of the study.