This book looks at how teachers implement national math and science standards in their classrooms. Teacher-authored chapters provide insights into how children think and reason as they pose questions, collect data, and build data models to answer their questions. While the spotlight is primarily on student understanding and its development over time, the text also highlights teachers' professional development of a specific form of knowledge. Chapters include: (1) "Children's Work with Data" (Richard Lehrer, Nancy D. Giles, and Leona Schauble); (2) "How Children Organize and Understand Data" (Angie Putz); (3) "How Much Traffic? Beep! Beep! Get That Car Off the Number Line!" (Jean Gavin); (4) "What's Typical? A Study of the Distributions of Items in Recycling Bins" (Carmen Curtis); (5) "Shadows" (Susan Wainwright); (6) "Graphing" (Jennie Clement); (7) "Graphing Artistry: Data Displays as Tools for Understanding Literary Devices" (Deborah Lucas); (8) "Data Models of Ourselves: Body Self-Portrait Project" (Erin Diperna); and (9) "Classification Models Across the Grades" (Sally Hanner, Eric James, and Mark Rohlfing). (MM)