This document discusses using assessment for learning in mathematics teaching. It focuses on collecting student data through tools like the Nelson Assessment Kit to inform lesson planning and differentiation. The goal is to gather clear evidence of individual student attainment in order to provide precise feedback and determine what each student needs to improve. If teachers commit to peer assessment and using student data to guide instruction, student engagement, learning and achievement will increase. The document encourages establishing transparent criteria and grading systems so students understand expectations and can coach each other.