Reasoning and Sense Making in the Mathematics Classroom, Grades 6–8, based on extensive research conducted by the authors, is designed to help classroom teachers understand, monitor, and guide the development of students’ reasoning and sense making about core ideas in middle school mathematics. It describes and illustrates the nature of these skills using classroom vignettes and actual student work in conjunction with instructional tasks and learning progressions to show how instruction can support students in their development of these competencies. Students who can make sense of mathematical ideas can apply those ideas in problem solving, even in unfamiliar situations, and can use them as a foundation for future learning. Without this base of conceptual understanding, students are reduced to rote learning, often experiencing frustration and failure. But what do reasoning and sense making look like in learning and teaching?Each chapter of Reasoning and Sense Making in the Mathematics Classroom, Grades 6–8 explores a different topic that children encounter in mathematics, demonstrating with actual student work and classroom dialogue how their mathematical knowledge and reasoning ability move through “levels of sophistication,” or learning progressions:After opening with a discussion of the nature of reasoning and sense making and their critical importance in developing mathematical thinking, chapter 1 examines how students attempt to make sense of the concepts of fractions and geometric properties of shapes. Chapter 2 discusses how reasoning about ratios and proportional relationships involves deep understanding of the multiplicative relationships embedded in the comparisons of two quantities. Chapter 3 focuses on what it means to call algebra a “style of mathematical thinking” and illustrates how students can view it as a reasoning and sense-making activity rather than as an isolated set of concepts to be memorized without understanding and quickly forgotten. Reasoning and sense making are inextricably linked in statistics and probability. Discussion and examples are used in chapter 4 to illustrate pedagogical practices that recognize and address students’ development of statistical understanding, including some of the misunderstandings that students display along the way. Chapter 5 examines how students make sense of and reason about decomposing shapes, and discusses the mental processes underlying this reasoning in the context of area, surface area, and volume. Not just a theoretical treatise, the book provides specific suggestions for related instructional activities for each topic. Reasoning and Sense Making in the Mathematics Classroom, Grades 6–8 will be a valuable and practical addition to your professional library.