Classrooms in our nation's schools reflect an "assembly-line model" of work in which the educational product is a set of students' performance and abilities learned in school. Contemporary educators are critical of the old factory model and seek to replace it by classrooms whose goals are to learn and to develop knowledge. Studied is the case of third-grade teacher Keisha Coleman, who, during the 1989-1990 school year, revised her views of the learning and teaching of mathematics and significantly changed her teaching practice. Beginning in October, the researcher spent 1 day a week in Ms. Coleman's mathematics classroom. Her lessons were observed, classroom discourse was audiotaped, and Keisha was interviewed after each lesson about how and what she was trying to teach, why she was trying to teach it, and what she hoped that the students would get out of the lesson. Reported here is a mathematics lesson taught by Keisha in November 1989, focusing on several major revisions that occurred in her mathematics teaching. She moved away from "teaching as telling" and moved towards guiding discussions as students figured out solutions to mathematical problems for themselves. Rather than focusing on covering mathematical content, Ms. Coleman focused on solving mathematical problems and discussing students' solutions and explanations. The ways that Keisha revised her thinking about teaching are discussed and possibilities for further revisions in her thinking. (KR)