The importance of teachers' influence is confirmed by a recent survey the author and his colleagues conducted of more than 300 teachers and administrators representing a mix of urban, rural, and suburban schools. In analyzing responses to an open-ended question about the greatest influences on respondents' professional practice, they found that internal factors (such as students, personal experience, colleagues, and family) had a greater influence than external factors (such as professional development, formal school leadership, and curriculum). In response to a follow-up question about the degree of influence, direct modeling by colleagues was the most powerful factor by far. Does this mean that the teacher next door is potentially more influential than books and lectures? Yes. The myth that professional development programs and lectures are sufficient to change professional practice has been challenged before. Despite the evidence, however, many schools ignore the power of direct modeling by classroom teachers as the key to high-impact professional learning. In this article, the author presents some practical ways that one can translate the research about teacher leadership and modeling into action.