Running cars down ramps: learning about learning over time

Any episode of learning and teaching is necessarily situated in both space and time. But, whereas the spatial arrangement of the classroom remains relatively constant, change is the very essence of the learning that takes place within it. Such is the nature of the data to be examined in this paper. The same curriculum unit was taught by the same teacher to a fourth-grade class in four successive years and every lesson in each year was videorecorded. Our purpose was to document change over time at three levels: from year to year, within each year, and over the course of activities within particular lessons. Within the limits of this paper, we focus on one particular issue as it recurred over time. 5