Formative assessment is designed to give students and teachers feedback on student progress towards the development of knowledge, understanding, and skills. This session focuses on the power of using formative assessment strategies to build on student understanding and to guide instruction toward student mastery of the mathematics learning goal. This session is designed to highlight pedagogies that align the T-TESS Rubric in the areas of Data and Assessment 1.2 and Content Knowledge and Expertise 2.2.