The purpose of this mixed method study is to examine what new principals say they learned and the sources of the learning that inform their thoughts and actions as instructional leaders. The research questions proposed for this study emphasize who (new principals), what (their espoused theories and theories in use as instructional leaders based on prior learning), where (high-stakes accountability environment), and how (they interpret their actions and the influence of those actions on the school culture and climate). The two research questions proposed for this study ask: (1) What do new principals say they learned about leading instruction? and (2) What were the sources of their learning? In this study, empirically-based standards and theories of meaning, learning, and action, provide an understanding of the origin of theories in action and are the foundation for instrument development and qualitative analyses on the link between the sources of acquired knowledge, espoused theories, and theories in use. This study found that new principals gave an extensive body of information on their knowledge of the critical components necessary for effective instructional leadership practice. They also highlighted areas in which more information and more training was necessary, with regard to dealing with people and being able to effectively communicate and mandate. Principal actions revealed new principals were putting knowledge into practice (espoused theory matched theories-in-use); yet, not in the amount necessary for strong instructional impact. Sources of learning were obtained from preparation programs, professional development models, and through their own adult learning. Yet, new principals also gathered information from direct experience, independent educational research, independent reading, and from personal attributes. The study implies that learning is still occurring throughout the first years within the principalship, which can account for the variations that are evident in principals' abilities to practice what they know about good instruction. Findings suggest that more initiatives need to be developed that take into account the importance of engaging aspiring principals in hands-on direct experiences prior to the principalship. It also suggests that new principals need more training in learning how to establish effective interpersonal relationships. [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.]