depth. Conversely, students' learning suffers when their experiences have no particular order and do not require or capitalize on earlier learning (NRC, 1999b). This does not mean that a student who has missed one or more units should not be allowed to progress. There are many alternative and creative ways to assist students to progress when some elements of important prior knowledge are missing.
This assumption echoes the central theme of both the NSES and the NCTM Standards, i.e., the content described in both documents is for ALL students.7 This report focuses on curriculum programs that will make that learning possible. Regardless of the source, an agreed-upon set of learning targets to be met by all students over a given amount of time (such as grades K through 12 or any other multi-year period) is a key element in the design of an effective curriculum program.
Teachers adapt and modify most curricula and instructional materials before and during use in the classroom. Even though the intended curriculum may vary from the delivered curriculum, there is ample evidence that the intended curriculum still has a significant effect on what is presented and learned (Schmidt et al., 1998).
In addition, the authoring committee acknowledges that the effort to improve mathematics and science education at the K-12 level must be embedded in a systemic context. In systemic reform, goals, standards, instructional materials, teaching practices, professional development opportunities, and assessment practices all are aligned with one another. In systemic reform, educational agencies adopt policies for the establishment and alignment of high-quality programs in curricula, teaching, assessment, professional development, and systems of support (Smith & O'Day, 1991; O'Day & Smith, 1993). The shaded and non-shaded portions of Figure 3 show key aspects of the system.
As noted in the "Introduction," this report addresses the steps leading to the design of the curriculum program, represented by shading in Figure 3. It does not address professional development, large-scale district, state, or national assessments, and support systems represented by the non-shaded