This book contains a carefully selected and adapted set of lessons from NCTM's Navigations series, with particular emphasis given to incorporating the Mathematics Teaching Practices in NCTM's Principles to Actions: Ensuring Mathematical Success for All. Teachers of students in grades 9–12 can use these lessons to help their students build on the foundation of their earlier education, expand their mathematical thinking into new areas, and advance in understanding and confidence. Each of the 12 Activity Gems includes the following elements:An overview of how the lesson can help students in grades 9–12 develop their mathematical knowledge and abilities, with lists of goals to achieve and all needed materialsA detailed three-part lesson plan—designed to Engage, Explore, and Extend—including questions a teacher can pose, challenges that students may face, and ways to continue the learning beyond the activityActivity sheets, classroom images to display, and any other necessary materials, all available both in an appendix and in downloadable and printable form at NCTM's more4U website