Faced with the forces of standardization and accountability, some teachers of young children succumb to prescriptions and pacing schedules that fail too many children, while others are able to teach in ways that are responsive to the children and families they serve. What distinguishes teachers who maintain a child-centered stance in the face of standardization? The term "teacher agency" has been applied to such teachers and their work. But does "agency" accurately represent who these teachers are and what they do? In this paper, we bring together definitions of agency in the literature; then we test these definitions against the work of novice teachers to instantiate the concept of agency with concrete examples from their work. And finally, we speculate on the usefulness of agency as a conceptual tool for thinking about how to prepare and support teachers who will remain faithful to and act on their child-centered convictions. (Contains 5 tables.)