models of these phenomena (e.g., Roberts and Barclay, 1988). These speculations are now being tested in classrooms with technology-based modeling tools. For example, the STELLA modeling environment, which grew out of research on systems dynamics at the Massachusetts Institute of Technology (Forrester, 1991), has been widely used for instruction at both the undergraduate and precollege level, in fields as diverse as population ecology and history (Clauset et al., 1987; Coon, 1988; Mintz, 1993; Steed, 1992; Mandinach, 1989; Mandinach et al., 1988).
The educational software and exploration and discovery activities developed for the GenScope Project use simulations to teach core topics in genetics as part of precollege biology. The simulations move students through a hierarchy of six key genetic concepts: DNA, cell, chromosome, organism, pedigree, and population (Neumann and Horwitz, 1997). GenScope also uses an innovative hypermodel that allows students to retrieve real-world data to build models of the underlying physical process. Evaluations of the program among high school students in urban Boston found that students not only were enthusiastic about learning this complex subject, but had also made significant conceptual developments.
Students are using interactive computer microworlds to study force and motion in the Newtonian world of mechanics (Hestenes, 1992; White, 1993). Through the medium of interactive computer microworlds, learners acquire hands-on and minds-on experience and, thus, a deeper understanding of science. Sixth graders who use computer-based learning tools develop a better conceptual understanding of acceleration and velocity than many 12th-grade physics students (White, 1993); see Box 9.3. In another project, middle school students employ easy-to-use computer-based tools (Model-It) to build qualitative models of systems, such as the water quality and algae levels in a local stream. Students can insert data they have collected into the model, observe outcomes, and generate what if scenarios to get a better understanding of the interrelationships among key variables (Jackson et al., 1996).
In general, technology-based tools can enhance student performance when they are integrated into the curriculum and used in accordance with knowledge about learning (e.g., see especially White and Frederiksen, 1998). But the mere existence of these tools in the classroom provides no guarantee that student learning will improve; they have to be part of a coherent education approach.
Technology can make it easier for teachers to give students feedback about their thinking and for students to revise their work. Initially, teachers working with the Jasper Woodbury playground adventure (described above) had trouble finding time to give students feedback about their playground