This empirical study explores the influence of developmental maturity on highly effective teaching. Viewing the K-12 classroom as a small social organization and positioning the teacher as leader of these organizations, this study brings together organizational development, constructive developmental theory, and education literatures to provide greater insight into the study of teacher effectiveness. Through the lens of constructive developmental theory, this study explored the ways in which six highly effective high school English Language Arts teachers make meaning of their experiences and how that meaning-making influences classroom practice. Through detailed case analyses and identification of each participant's action-logic, this study considers both the transformational growth experienced by these teachers, as well as the transformational impacts they have on their students. The identification of the action-logics present in this study sets it apart from other studies of highly effective teachers. Each of the participants assessed at mature, self-authoring developmental stages (Achiever and Redefining). The data suggest that the capacities associated with these mature stages do influence how these teachers exercise leadership in the classroom, understand their role, and go about their work. The results of this study have significant implications for transforming teacher preparation and professional development programs. It serves as a foundational step in the exploration of the influence of teacher developmental consciousness as it relates to teacher performance. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]