to support the curriculum often correlates to textbook-adoption cycles but may also be subject to uncertain budgets. It is not uncommon for an adopted textbook to remain in use for five to eight—or even ten—years; a text selected in 1995 could still be in use in 2005.
Teachers sometimes select materials that conform to their own beliefs about teaching, despite district curriculum guidelines or the changing nature of the subject (Grossman and Stodolsky, 1995; CCSSO, 2000). Decisions about instructional materials may be influenced by public and community preferences or by achievement results on high-stakes assessments (Massell, Kirst, and Hoppe, 1997; Battista, 1999; Anderson and Helms, 2001; Becker and Jacob, 2000). Decisions may also be influenced by endorsements of federal agencies (USDoE’s Mathematics and Science Expert Panel, 2000) or by curriculum evaluations published by nongovernmental groups such as the American Association for the Advancement of Science (AAAS) Project 2061, the Mathematically Correct, or the American Institute of Biological Sciences (AIBS)(AAAS, 2000; Clopton et al., 1998; Morse and the AIBS Review Team, 2001).
In about twenty states, including many in the South and West, a statewide selection process for instructional materials, usually guided by state specifications for student learning, leads to lists of state-approved textbooks, with one or more titles specified for each discipline and grade level (Weiss, 1991; Tyson 1997). Once a particular instructional program is placed on a state-adoption list, funds allocated by the state for instructional materials can be accessed by districts and schools to purchase that curricular program.
At the district level, the selection and purchase process for instructional materials is highly idiosyncratic. The nature of adoption mechanisms for instructional materials depends, in part, on the level of human and fiscal resources available to districts or schools. In some instances, a formal process specifies development