This book outlines Cooperative Small Group Discovery (CSGD) theory and practical learning strategies for implementing it in secondary and collegiate classrooms. Based on Neil Davidson's decades of work, the author team has designed a resource to help current users of small group methods in mathematics refine their practice and to entice others to try the strategies themselves. The book describes principles and strategies for teaching, complemented by an extensive collection of examples from instructional materials designed to support teacher implementation, with a focus on topics in the algebra curriculum. Chapters are organized into four parts, beginning with the theory and practice of CSGD and moving through examples and guidance, both on sequencing CSGD activities into unit plans and addressing challenges of CSGD in the classroom. The authors outline the rationale and basic operational principles of teaching through CSGD, as well as common student and teacher roles accompanied by a variety of structural models to illustrate these roles. The authors also include lesson plans that show how students can develop an understanding of elementary and advanced algebra through problem-based CSGD, and how coherent units of CSGD material can be used to develop student understanding of key ideas about linear and quadratic functions. The authors complement this information with practical strategies for getting started with cooperative small group discovery teaching, some common challenges in using small group methods, and proven methods for solving those problems. Ideal for educators and faculty involved in secondary and collegiate mathematics instruction, this resource develops teacher understanding of principles and methods of cooperative learning and provides practical advice on getting started and refining that work.