Professional growth is a complex process that requires thoughtful planning, persistence in execution, collaboration, and a common goal if it is to be successful. Classroom teachers have many opportunities to participate in professional development, but experiences vary and it is important to determine which have the greatest effect. The purpose of this comparative study was to examine the strengths and differences of three models of professional learning communities involved in a three-year project to improve writing instruction in kindergarten to Grade 3 classrooms. Based on the work of Routman (2008a), professional staffs at treatment schools were involved in a multi-year, inter-divisional, professional learning community. Teachers and principals in the project participated in one of three experiences of varying intensity. Results are compared to a control group of schools. The study design takes a pragmatic worldview and utilizes mixed methodology to conduct an ex post facto, quasi-experimental analysis. Artifacts collected from 2009 to 2012 include questionnaires, written self-evaluations, and samples of student writing, that were examined to determine the degree and nature of change in principals’ increased perceptiveness of the school literacy team, teachers’ increased sense of efficacy in writing instruction, and significant changes in student writing. These are compared to samples from a control group of schools that were not involved in the experience. Several aspects of this multi-year project bring to light three critical observations. First, real-time, live experiences with an expert facilitator have a dramatic effect on teacher learning. Second, students in the first four years at school are capable of much more sophistication in writing than is generally expected. Third, principals’ involvement as educational leaders is critical to enduring teacher change and ongoing student improvement. / February 2017