ductory Physical Science and Project Physics. By 1975, NSF supported 28 science curriculum reform projects.

By 1977 over 60 percent of school districts had adopted at least one of the new curricula (Rudolph, 2002). The PSSC program employed high school teachers to train their peers in how to use the curriculum, reaching over half of all high school physics teachers by the late 1960s. However, due to implementation problems that we discuss further below, most schools soon shifted to other texts, and the federal goal of attracting a larger proportion of students to undergraduate science was not achieved (Linn, 1997).

Dissemination of the NSF-funded curriculum development efforts was limited by several weaknesses. Some curriculum developers tried to “teacher proof” their curricula, providing detailed texts, teacher guides, and filmstrips designed to ensure that students faithfully carried out the experiments as intended (Matthews, 1994). Physics teacher and curriculum developer Arnold Arons attributed the limited implementation of most of the NSF-funded curricula to lack of logistical support for science teachers and inadequate teacher training, since “curricular materials, however skilful and imaginative, cannot ‘teach themselves’” (Arons, 1983, p. 117). Case studies showed that schools were slow to change in response to the new curricula and highlighted the central role of the teacher in carrying them out (Stake and Easley, 1978). In his analysis of Project Physics, Welch concluded that the new curriculum accounted for only 5 percent of the variance in student achievement, while other factors, such as teacher effectiveness, student ability, and time on task, played a larger role (Welch, 1979).

Despite their limited diffusion, the new curricula pioneered important new approaches to science education, including elevating the role of laboratory activities in order to help students understand the nature of modern scientific research (Rudolph, 2002). For example, in the PSSC curriculum, Massachusetts Institute of Technology physicist Jerrold Zacharias coordinated laboratory activities with the textbook in order to deepen students’ understanding of the links between theory and experiments. As part of that curriculum, students experimented with a ripple tank, generating wave patterns in water in order to gain understanding of wave models of light. A new definition of the scientific laboratory informed these efforts. The PSSC text explained that a “laboratory” was a way of thinking about scientific investigations—an intellectual process rather than a building with specialized equipment (Rudolph, 2002, p. 131).

The new approach to using laboratory experiences was also apparent in the Science Curriculum Improvement Study. The study group drew on the developmental psychology of Jean Piaget to integrate laboratory experiences with other forms of instruction in a “learning cycle” (Atkin and Karplus, 1962). The learning cycle included (1) exploration of a concept, often through a laboratory experiment; (2) conceptual invention, in which the student or



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