Hands on!

F and second graders watch a toy car roll down a ramp. The students, in this economically and racially heterogeneous classroom, are working to develop qualitative descriptions of the car’s motion, specifically, changes in its speed as it moves down the ramp. Sharrone, a child who has rarely spoken since the first day of school, volunteers, and holds the floor for nearly ten minutes as he explains what he thinks is happening. Using an analogy to describe the car’s motion, he imagines a bike going down a high hill, going faster and faster, not able to stop, hitting a passerby near the bottom of the hill and sending her to the hospital. His teacher asks him to explain why the bike might hurt the passerby, anticipating some account of the bike’s fast speed. Sharrone responds with more elaborate details of the event, explaining how the bicyclist and the