Book excerpt: This book traces the origins and activities of the longest-standing collaborative teacher group in education, the Portfolio Group. Each chapter documents, historically and conceptually, the main intellectual moments in the evolution of the idea of knowledge communities. Authors illuminate the expansive work, research, and the leading/learning influence that the Portfolio Group has had in the local education community as well as on the international education landscape. In doing so, they illustrate the journey of a school-based, cross-institutional knowledge community and provide the proverbial light at the end of the tunnel for so many novice and newly formed groups seeking sustainability. The book demonstrates through the shared experiences of five teachers/teacher educators the ways in which varied collaborations aimed at professional development lead to teacher growth in practice, leadership, and career.