features, and we use them to illustrate some key points, although they may fall short in other regards. It was not possible to include examples from all of the state standards that meet a particular criterion, and many examples could be found of other state standards that meet many of the criteria we discuss. Similarly, our including a state’s standards in this document does not constitute an endorsement by the committee of that state’s standards as a whole.

Clear, Detailed, and Complete

To serve as the basis for curriculum development, the selection of instructional resources, and related activities, science standards must describe the desired outcomes of instruction in clear, detailed, and complete terms. Clarity is important because curriculum developers, textbook and materials selection committees, and others need to develop a shared understanding of the outcomes their efforts are designed to promote. If the standards are incomplete—for example, if they omit important aspects of science—the curriculum will contain similar gaps. We do not suggest that, to be complete, standards should include everything that is known about student learning in this area. That would be both impractical (since it would lead to encyclopedic standards documents) and impossible (since understanding of student science learning is still developing). Rather, we suggest that the standards should reflect careful judgment about which aspects of science students need to learn. One means of paring this very large domain down to a manageable size to serve as targets for instruction and assessment is described by Popham et al. (2004) (see Chapter 2, the instructionally supportive design team model).

However, completeness means more than covering the important science content. It also means providing enough information to communicate a standard well. For example, a complete description of a standard should include as much information as possible about related concepts and principles that are necessary for students to develop an understanding of the standard, prerequisite knowledge that students will need, subsequent knowledge that will build on the standard, expectations for student performance that demonstrates mastery of the standard, and connections to related standards. Sufficient detail is necessary to enable educators to determine whether potential curriculum units and materials promote the goals that the standards are supposed to represent. This is best communicated by concrete examples of student work at all levels of achievement.

In addition, the standards must provide a complete description of the domain of science as a school subject. If standards are incomplete, they will not provide a common reference for all users. One way that standards can be incomplete is by using broad, general, or vague language that leaves interpretation to the individual. This defeats the purpose of having standards. When describing student performance objectives, if standards use precise terms, indicating whether students are expected to know, explain, communicate about, compare, differenti-

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