This collection of lessons from experienced teachers provides multifaceted examples of rigorous learning opportunities for mathematics students in Grades 6–12. The four sample units focus on fractions, linear programming, geometry, and quadratic relationships. The authors provide user-friendly methods for instruction and demonstrate how to differentiate the lessons for the benefit of all students. Included are standards-based strategies that guide students through: • Understanding secondary mathematics concepts • Discovering connections between mathematics and other subjects • Developing critical thinking skills • Connecting mathematics learning to society through the study of real-world data, proportional reasoning, and problem solving