would appear in chapter 4 if the components were emphasized equally, or presented in an integrated format. In other words, the placement of an annotation in a particular chapter in this guide simply attempts to reflect the emphasis in the unit itself. To locate annotations, readers can refer to the various indexes in the guide, including the index of topics in the curriculum materials and the index of scientific areas and categories of the curriculum materials, by grade level.

The Organization of Materials in Chapters 1-4

The annotations in the curriculum chapters are placed in categories that can be identified as three major levels of materials in teaching hands-on, inquiry-based elementary school science:

• Core Materials

• Supplementary Materials

• Science Activity Books

This grouping allows readers organized and easy access to the full array of materials presented in each scientific area. Descriptions of what constitutes "core," "supplementary," and ''science activity books" for the purposes of this volume are as follows:

• Core materials are substantial enough to form the foundation of an effective elementary school science curriculum. They (1) focus on concept development and understanding; (2) allow students to study a subject in depth over an extended period of time—typically 6 to 8 weeks, depending upon the grade level; (3) are grade-level specific (that is, they were developed for science classes in one, or at most two, specific grade levels); and (4) include a variety of assessment activities that are aligned with the goals of hands-on, inquiry-based science teaching and learning as an integral part of the module.

• Supplementary materials are activity-centered units judged to be supportive of inquiry-based science teaching that fosters understanding of science concepts through hands-on student investigations. Although these materials provide support and enrichment, they do not have the depth or focus of core units.

• Science activity books offer excellent hands-on science activities for children. Such books provide practical ideas for facilitating science learning but are often too broad in scope or too specific in focus to serve as the foundation of an elementary science program. These materials can be used, however, as supplements to existing curriculum or as independent investigations to enhance children's experience of science.

Placing the materials in categories implies no judgment as to the quality, merit, or desirability of any particular title. All of the materials annotated here are considered to be effective teaching materials.