The Colorado Study (Lance, Wellborn, and Hamilton-Pennell 1993) and its many replications in other states have demonstrated that when educators and learners had access to a qualified school librarian in the context of a thoughtfully built, adequately resourced, technology rich, and widely accessible school library, learners tended to flourish on traditional measures of reading and science achievement, regardless of the district or community's relative wealth and other external factors (Scholastic 2016). This correlational research has been vital for communicating the value of school librarians and school libraries to decision makers and other stakeholders. The Causality: School Libraries and Student Success II (CLASS II) project is aimed at establishing the foundation for comparison and groundwork for causal research. In this article, the authors share the CLASS research agenda and progress to date and demonstrate how this effort to chart the future of school librarianship research has the potential to guide and strengthen professional growth and implementation. The resulting knowledge is to help school librarians create meaningful, authentic learning experiences that impact and influence the next generation of learners.