Formative assessment is a planned process that uses assessments to inform changes in instruction or learning. Because of its focus on instruction and learning, formative assessment is based in the classroom, although school-level structures, such as learning communities, can support the process. In this article, the author presents seven stepping-stone "understandings" that secondary school principals need to possess if they wish to add formative assessment to their leadership repertoires. In concert, these seven understandings will contribute to successful formative assessment.