Organizational systems have worked towards optimizing their processes and resources, but our complex education system is struggling to follow suit, toiling with which critical foundations must be in place for schools to run optimally, enabling them to successfully and authentically meet the needs of their students and of the unique communities they serve. Due to decades of implementation failure, there is a need to study what works and uncover what is missing from improvement efforts that fail. This study aimed to theoretically connect and confirm what past and current research has demonstrated about the relationships between school leadership, culture, and expertise, and how these variables contribute to the optimization of educational organizations. The empirical aim of this work was to propose and support a model for whole school optimization to bridge the gap between educational research and best practices to inform school leaders and policy makers about more effective methods with a tool to guide their efforts. An extensive literature review led to one overarching hypothesis: school leaders are the critical component in the system who are responsible for creating a culture that utilizes irreplaceable, expert teachers in innovative leadership roles to have a significant positive impact on creating sustainable, authentic change. This hypothesis was tested through a sequential, mixed-methods, multiple case study approach designed to identify the relationships between school leadership, school culture, and teacher expertise in reaching optimization in authentic school improvement. Two different sample populations were studied in three phases. The sample of participants for Phase I of this work was a random selection of educators who completed and submitted an online survey that collected both quantitative and qualitative data. The participants of Phases II and III were purposefully selected school leaders, teachers, and staff who worked at schools that had demonstrated a history of success and were led by principals who had been recognized and honored for their leadership abilities. In addition to the qualitative data collected from the online survey, Phase III participants contributed additional qualitative data through interviews, observations, and the collection and documentation of artifacts. The findings of the study, though not generalizable to larger populations due to its small sample size, are significant because they support and confirm the theoretical model proposed by the researcher. This work is significant for multiple reasons. First, it identifies school leaders as an integral part of a system that serves as the catalyst to creating and supporting a culture of capacity building and purposeful collaboration to overcome barriers and achieve success in improvement efforts. It also supports that school leaders must be able to identify irreplaceable, expert teachers to utilize them in innovative roles in the school improvement process. Finally, this work connects educational systems with other complex systems who use the whole systems approach to solving wicked problems. The major findings of this work support the positive connections between effective school leadership, school culture, teacher expertise, and authentic school improvement. The Whole School Optimization Model proposed in and supported by this research is a viable model to inform educational leaders on how to successfully overcome the complex problems they face through the identification and utilization of expert teachers in their authentic school improvement efforts. From this research new, additional terms can be added to the existing body of knowledge on school leadership, teacher expertise, and school improvement: withitness, purposeful collaboration, authentic school improvement, and wicked problems in education. This study will inform teachers, school and district administrators, and policy makers on how to best utilize their human resources and system structures to build professional capacity that will create and sustain positive change, and ultimately optimize K-12 school organizations through authentic school improvement. [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.]