The scientific practices at the heart of the biodiversity work took place both outside and inside the classroom. In addition to fieldwork in the schoolyard (mapping, observing, drawing, plotting frequency), the students actively participated in discussions about their data, their questions, and their emerging conjectures and plans for systematically following up on these ideas. Students worked in small groups and regularly engaged in “cross-talk” sessions in which they exchanged information with other interest groups. And of course there were the monthly biodiversity conferences, moderated by Mr. Walker and Ms. Rivera. On the basis

of both fieldwork and class work, the groups spent a great deal of time refining, revising, and publishing their work so that they could share it with others—other classes in the school, local experts, and members of the community.

The monthly meetings of the two groups were designed to be like scientific conferences, and the students treated them with appropriate seriousness and respect. Attendance was nearly 100 percent on these days in both classrooms, and the students rarely misbehaved. They spent a great deal of time and effort preparing their presentations.

A major point of controversy that played out in the biodiversity conferences involved the question of what defines a “weed.” The conclusion that defining a weed was more a matter of interpretation and perspective, as opposed