This work highlights a heuristic model for professional learning while examining the implementation of a reform initiative. The researchers used longitudinal data collected from surveys to develop and fit a model of professional learning where patterns of interaction among teachers changed the discussion about English learner instruction. Data were collected over two years from an English learner reform initiative. By aligning the organizational constructs of a reforming middle school to the implementation of an English learner initiative characterized by a heuristic model for professional learning, the authors appraised the relative influence and informal processes that occur in teacher professional development.