The participants in this study were teachers and students of a large school district located on the east coast of Canada. We distributed surveys to 1,514 teachers across 84 schools and received 1,423 usable surveys for a return rate of 94%. At the time of the second data collection, three years later, 1574 teachers from 78 schools agreed to participate. Teachers' perceptions of their schools as professional learning communities were assessed using 32 items in a 5-point Likert format. The responses to the 2006 survey were factor analyzed using ML estimation. A number of different factor structures were tested, including a single factor model and a second-order factor analysis. In spite of a heavy emphasis by school board leaders and the collaborative development, introduction, and implementation of PLC practices before and during the study period, no significant measurable effect on student learning was identified.