Districts across the country are currently adopting models of professional learning communities (PLCs) as a means for improving teachers' instructional practice and student achievement. This evaluation research case study shares the 3-year history, development, and challenges of a district-wide implementation of Critical Friends Groups (CFGs), a particular format for PLCs. Using Argyris and Schon's (1974) theories of action framework, the authors identify teachers' espoused theories about a contextually situated CFG initiative and examine teachers' conceptualizations about the ways in which their work influences the progression and effectiveness of this professional development model. Findings from this study suggest that the degree to which the CFG implementation model is integrated with other school improvement initiatives, specifically those that address teachers' professional development, dramatically influences how key stakeholders conceptualize and draw the necessary connections to their roles in improving instructional practice and addressing student achievement and learning.