This paper sets forth implications for staff development of a social constructivist perspective on school teaching, learning, and subject matter. The perspective is illustrated by an overview of the research-centered staff development work done in the beginning months of the Teachers' Conceptual Change in Practice Project. In the first half of the paper the author provides an overview of the staff development approach and defines key concepts of narrative understanding and enacted curriculum. The second half of the paper presents a social constructivist model of the social and academic dimensions of classroom tasks and illustrates the model with an example of a first-grade seatwork assignment. The paper argues that effective teaching necessarily involves mutual adaptation by teacher and student so that the social and academic task presented to the student fits the student's current mode and level of functioning. This adaptation requires the teacher's capacity through narrative understanding to conduct fine-tuned, on-the-spot analysis of the enacted curriculum of the moment as it is being experienced by students, and it also requires the teacher to possess the authority to alter classroom tasks to fit the learners who confront the tasks. The paper focuses more on the nature of the classroom tasks, and on teachers' understanding of and options for their construction, than it does on the notion of time spent by students in working at tasks. A two-page list of references concludes the document. (Author)