... It can be difficult for teachers to undertake the task of rethinking their subject matter. Learning involves making oneself vulnerable and taking risks, and this is not how teachers often see their role. Particularly in areas like mathematics and science, elementary teachers often lack ... , and they worry about admitting that they don’t know or understand for fear of colleagues’ and administrators’ reactions (see, e.g., Heaton, 1992; Ball and Rundquist, 1993; Peterson and Barnes, 1996; Lampert, 1998). In addition, teachers ... are accustomed to feeling efficacious—to knowing that they can affect students’ learning—and they are accustomed to being in control. When they encourage students to actively explore issues and generate questions, it is almost inevitable that ... will encounter questions that they cannot answer—and this can be threatening. Helping teachers become comfortable with the role of learner is very important. Providing them with access to subject-matter ... is also extremely important. New developments in technology (see Chapter 9) provide avenues for helping teachers and their students gain wider access to expertise....