The purpose of this qualitative case study was to examine one public elementary school in Spokane, Washington that has received significant complex trauma professional development training provided by Washington State University Area Health Education Center (WSU-AHEC). The study explored teachers', specialists', and the principal's perceptions of the impact of complex childhood trauma professional development training on the school-wide programs and practices, and classroom practices at Willow Elementary School (pseudonym). This study also examined the role of school leadership in supporting staff efforts to create a trauma-informed/trauma-sensitive learning environment. The specific research questions that guided this study are: (a) What is the impact of the complex childhood trauma training on the teachers, specialists, and principal in regard to their school-wide programs and practices and classroom practices? (b) How has the complex trauma professional development training influenced the beliefs about and responses to children who have experienced traumatic events?, and (c) What is the role of leadership in supporting teachers "and specialists" abilities to respond appropriately to children who have experienced complex trauma? Face-to-face interviews, observations, and a collection of documents were used as data sources for the study. Analysis of the data resulted in three major themes. The first theme, "implementation of trauma-sensitive programs and practices," explored the impact that the WSU-AHEC complex trauma training has had on classroom and school-wide practices. The second theme, "the power of 'WE,'" examined the collective beliefs of staff that serve as the anchor for the complex trauma work. The third theme, "leadership matters", spotlighted the role of leadership in creating, fostering, and supporting a trauma-sensitive learning environment. The findings from this study suggest four main conclusions: (a) Complex trauma professional development training appears to be extremely valuable in supporting school staff as they create a trauma-sensitive learning environment; (b) two critical aspects of a trauma-sensitive school are building relationships with children and creating a safe and predictable learning environment; (c) leadership support is an essential component to creating a trauma-sensitive school; and (d) successfully meeting the needs of children who have experienced traumatic life events is difficult work that requires a collaborative school culture. [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/en-US/products/dissertations/individuals.shtml.]