This article presents a guide to the development of formative assessments for school librarians participating in professional learning communities (PLC). It describes librarians' reading of assigned books, meeting with their PLCs, and incorporation of learned strategies in their daily instruction. Central library service readers' regular visits to schools to monitor librarians' use of learning targets are also described. Based on a book study of "Seven Strategies of Assessment for Learning" by Jan Chappuis (2009), the PLCs learned strategies, presented herein, that they would practice using formative assessment in the library setting.