This article provides an opportunity to extend the discussion about teacher communities as part of complex school reform models, specifically centered on those communities whose membership is drawn on a semi-voluntary basis. Through a sixteen-month long ethnography, I document the activities of an urban teacher professional community (TPC) at a high school located in a large city in the Northeast, serving a majority of linguistically and culturally diverse students. Guided by Sharp and Green s definition of teacher ideologies, the study focuses on how TPC members negotiated curriculum, teacher learning, and student discipline, carrying ideologies that impacted the outcomes of the community's work, originally intended to increase teacher collaboration and foster quality teaching.