This chapter, by Kevin J. B. Anderson, shares examples from experiences that support teacher professional learning about scientific arguments based on evidence. The chapter also delves into strategies to help teachers build formative and summative assessments and to engage students in modeling as part of their explanations. Throughout the chapter, the importance of effective, cyclical professional development rather than one-time workshops is stressed. Teacher background information, standards, assessments, references, and resources are provided. This book selection also includes the Table of Contents, Foreword, Preface, Acknowledgments, and Index.