In order to evolve from traditional librarianship roles to dynamic and proactive leaders today's school librarians need to understand what it means to be a school librarian leader, build those skills, and advocate for new opportunities within their school communities. This qualitative investigation into the leadership behaviors of school librarian leaders contributes to the work of Everhart and Johnston (2016) by developing their definition in order to operationalize school library leadership through the documentation of what it looks like in practice. This research is among the first efforts to move a proposed model of school librarian leadership from a theoretical model to a working theory. A multi-case design compared and examined leadership behaviors as they occurred in practice. Interviews, observations, and documents, collected at three high school libraries in Maine, served as the primary methods for data collection. The findings support Everhart and Johnston's (2016) proposed theory that school librarian leaders intentionally develop strong relationships within the school community, serve as communication conduits in order to improve the school environment, and increase their confidence through mentorship from administrators and support from the school community. The findings extend the proposed theory by adding risk-taking, vulnerability, and job crafting as supports to the innovative work of school librarian leaders. This knowledge will help school librarians develop skills and an understanding of their updated role and prepare them to reach their full potential as school librarian leaders.