Ch. 1. "Mathematics" or "Mathematizing"? -- Learning and Teaching in the Classroom -- Teaching and Learning as Development -- Strategies, Big Ideas, and Models in a Teaching/Learning Framework -- Ch. 2. The Landscape of Learning -- Describing the Journey -- The Role of Context -- Turning Classrooms into Mathematical Communities -- Ch. 3. Equivalence on the Horizon -- Fair Sharing: The Historical Roots of Equivalence -- Measurement Contexts -- Expanding Commercial Markets as a Context -- Children's Strategies for Equivalence -- Ch. 4. Developing Big Ideas and Strategies -- Big Ideas on the Horizon -- Strategies on the Horizon -- Ch. 5. Developing Mathematical Models -- What Are Mathematical Models? -- Modeling Actions and Situations -- Facilitating the Development of Modeling: The Role of Context