This study is an interpretive investigation of Sarah, a first-time teacher of middle- and high-school science who, because of high levels of disruption, was unable to establish and maintain environments favorable to learning. Sarah reflected on her roles as a teacher and identified facilitating learning, management, and assessment as salient, each being associated with defining metaphors and belief sets. Sarah's efforts to improve her teaching began with the construction of a new metaphor, the social director, for her role as manager. She developed coherence between the new metaphor and beliefs about constructivism, teaching, and learning. Sarah then managed her class in accordance with the social director metaphor and, although improvements were apparent, some students were uncooperative. Sarah then changed her metaphor for assessment from the teacher being a fair judge to the teacher looking through a window into a student's mind, an opportunity for students to show what is known. When this metaphor guided Sarah's assessment practices the learning environment improved appreciably. Although the development of new metaphors was a significant part of the process of reconceptualizing her roles as a science teacher, Sarah could not have improved the quality of teaching and learning without substantial assistance from her colleagues and school administrators.