One strategy for implementing learner-centered teaching is through the preparation of teachers and their induction into the profession. This article presents case studies of three secondary science teachers that follow them from their science teacher education program that advocated teaching for conceptual change as one approach to learner-centered teaching into their first years of teaching. The article’s purpose is to describe the teachers’ initial conceptions of teaching science carried over from their teacher preparation program, and how they integrated those conceptions with the environmental influences of their classrooms and schools to produce praxis. Data were collected from the participants in several different ways during the participants’ pre-service year and during their first year or two of teaching: Observation of the participants’ teaching; related interviews with participants; and their action research journals. As they approached the end of their first or second year of teaching, all three teachers demonstrated increased levels of confidence in their teaching competence, both in their classroom performance and their places in their departments and schools. None of them had, however, fully implemented conceptual change teaching approach that was the specific goal of their teacher preparation program.