larly the degree to which they provide accountability, the IEP has become paramount in determining the services children with disabilities receive (Smith, 1990). Among other provisions, the IEP has generally determined whether or not a student will participate in testing programs, and if so, under what circumstances.
Participation in testing programs has varied. In addition to the number of students who have been excluded from tests, many others have taken tests that accommodate them in some way. States and districts generally employ four types of accommodations to tests (Thurlow et al., 1997):
As the National Research Council's Committee on Goals 2000 and the Inclusion of Students With Disabilities found, the number of students who need such accommodations is unknown. Moreover, the extent to which states and districts employ any or all of these accommodations varies widely, depending on the population of the state, the state's standards and assessments, and other factors (National Research Council, 1997a).
However, because most students with disabilities have only mild impairments, the vast majority can participate in assessments with accommodations. Only a small number of the most cognitively disabled students, whose educational goals differ from the regular curriculum, will be required to take alternate assessments under the IDEA.
Despite the common use of such accommodations, however, there is little research on their effects on the validity of test score information, and most of the research has examined college admission tests and other postsecondary measures, not achievement tests in elementary and secondary schools (National Research Council, 1997a).
Because of the paucity of research, questions remain about whether test results from assessments using accommodations represent valid and reliable indicators of what students with disabilities know and are able to do (Koretz, 1997). But a number of studies are under way to determine appropriate methods of including students with disabilities in assessments, including the National Assessment of Educational Progress (National Research Council, 1999a).