distinguish among these approaches risks the selection of materials inconsistent with district requirements. Yet, even experienced teachers may not perceive the goals of the standards when they occur in innovative materials (Bush et al., forthcoming).
Selection committees may choose materials without recognizing that their effective classroom use depends on providing teachers with extensive professional development in the pedagogical approach embodied in the materials. Such a situation arises, for example, if the materials represent an activity-based or inquiry-based science program, and the teachers have traditionally depended on textbooks and didactic lessons (Little, 1993).
A related issue is the influence of assessments. Assessment tools used in the school district need to be consistent with the learning goals, pedagogical approach, and assessments built into the materials (Webb, 1997).
Financial resources are almost always an issue. The amounts budgeted for instructional materials may not be sufficient to purchase desirable materials, and tradeoffs may be required. Budget restrictions may also result in the use of dated, even inaccurate, materials long after they should have been set aside.
Instructional materials are a primary source of science learning in the nation's classrooms. In high schools and middle schools, textbooks are essential supplements to the limited amount of material that can reasonably be presented in the classroom time available to the teacher. Packaged instruments and materials (kits) for laboratory and hands-on experiences are an enormous help to busy teachers at all levels, K-12. The availability of excellent instructional materials is critical for elementary school teachers who, in spite of minimal formal scientific education of their own, are called on to teach a range of scientific concepts from chemistry to natural history, earth science, astronomy, and ecology. The closer instructional materials adhere to the goals of state and national standards, the more likely the teacher is to succeed in achieving those goals.
Instructional materials influence the continuing professional development of teachers in several ways. For elementary school teachers, the materials often provide basic information on content and pedagogy. Formal professional