The experience, knowledge, and talents of teachers are the raw materials, the human capital which can be formed into teacher professionalism. Teachers and administrators working together can provide the human capital that teachers bring to their schools with a place to grow and mature into a workforce of professional teachers capable of providing students with opportunities for learning and education. This research assessed the impact of teachers, empowered by administrators employing distributed leadership as a theoretical lens in their practice and applying the definition of distributed leadership as capacity building to their practice, utilizing emerging practice to engage in a teacher designed professional learning task on the development of teacher professionalism through building a workplace climate and culture of collegiality and collaboration focused on instruction. Investigating via a mixed methods study, QUAN(qual), taking place over the course of a semester, this study had a one-shot experimental case study design. At a suburban high school in the Midwest, a participating administrator and a team of participating teachers generated data about the research site, participant demographics, and about the participants' research experiences. The data showed that participating teachers and the participant administrator agreed that participation in a teacher generated professional learning task via emerging practice worked to build a workplace climate and culture of collegiality and collaboration focused on instruction. Also, the data showed that the practice and leadership of participating teachers and of the participant administrator were positively impacted through participation in this research. These findings suggest effective means of teacher professional development. Areas for further research include using distributed leadership in the schoolhouse, providing teachers with leadership opportunities as teacher professional development, the role of professional learning tasks in teacher professional development, and the importance of context to teacher professional development. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]