The Pedagogy Primer raises questions and provides explanations that are central to the study and practice of teaching. Most educational research and policy, and even teaching practice, fails to recognize the complexities of pedagogy. This primer unearths the various histories, structures, and narratives that undergird teaching in U.S. schools. Modern teaching practice is revealed to be an uncritical historical layering of irreconcilable worldviews, intermixed with a craft or guild perspective, and undermined by cultural and political ideologies that promote one perspective at the expense of others. Understanding pedagogy requires sorting out these conflicting worldviews embedded in educational policy, research, and practice. Professionalism requires developing a personal schema for balancing the values of each worldview. This primer investigates the socio-cultural context and aims of teaching, pedagogical content knowledge, uses of disciplinary knowledge, and the epistemology and language of teaching. Aimed at new as well as experienced teachers, and innovative researchers and policymakers, the Pedagogy Primer is essential reading for those who study teaching and learning and those who engage in the profession of teaching.