This paper introduces the purposes of school learning communities. Section 1, "Foundations of a Learning Community," presents a definition and discusses different approaches to reforming schools. Section 2, "Key Aspects of a Learning Community," highlights three components of learning communities (student learning, teacher learning, and collaborative learning); new conceptions of learning for all students (developmental aspects of learning; learning transfer; novice, competent, and expert learners; environmental and social conditions to promote learning; expert teachers; technology; assessment; and new conceptions of learning and learning communities); and teachers as learners (developmental considerations, socially constructed teacher learning, structural conditions for teacher learning, teacher learning focused on the whole system, and bringing together multiple perspectives on teacher learning to enhance professional development and student outcomes). This section also discusses a collaborative culture (incentives and opportunities for collaboration to build knowledge, a climate favoring continuous school improvement, and transformational leadership by school principals). Section 3, "An Approach to Implementing Data-Based Decision Making," describes the KEYS (Keys to Excellence for Your Schools) initiative, which provides an instrument and guidelines for facilitating the self-study process. Section 4 presents "Suggested Readings." Two appendixes offer the NPEAT principles of professional development and a description of KEYS. (SM)