DescriptionTeacher professional learning communities (PLCs) are an increasingly common initiative to improve student achievement. This study applies literature about PLCs to understand the collaborative practices of one team of high school social studies teachers. The purpose of this study is to investigate one PLC’s development of common assessments. It examines the interactions between teachers during the implementation of the Common Core State Standards for History and Social Studies (CCSS). The study focused on the interactions among teachers during PLC time designated for teacher learning that improves student achievement. The problems examined included how teachers created and continued to use assessments aligned to the CCSS. This qualitative case study included three sources of data: PLC meeting notes, teacher-created common assessments, and interviews of teachers who participated in the PLC. Ten teachers and one supervisor participated in the interviews; two participants were interviewed twice. Three themes emerged from the data: the importance of developing a shared vision, the supportive nature of the school leader’s role, and the ways teachers networked for specific expertise to support their work. Implications that followed from the findings included how teachers benefitted from the leadership of their colleagues, time to work together on specific goals, continuous professional development designed around recommended changes, and resources directly related to their work. This study provides details to help school leaders facilitate teacher collaboration around assessments aligned to reading and writing skills in secondary social studies contexts.