Formative assessments are usually informal and can range from oral question-and-answer sessions in class to performance events or quizzes. Stiggens and DuFour (2009) state that teachers and schools should use formative assessments to clarify what students are supposed to be learning, improve the instructional practices of individual teachers, and allow for reteaching of concepts to reach struggling students. This article examines the results of an action research project and describes how it improved teaching and learning in one school district. (Contains 4 figures.)