The Education of the Handicapped Act, passed in 1975, was
changed to the Individuals with Disabilities Education Act (IDEA) in 1990,
and was reauthorized in 1997. IDEA (and its predecessor legislation)
resulted in fewer students with disabilities being educated in separate
schools or classrooms. The effect of this change has at least two methodological implications. First, identification of research subjects became more
complicated, and second, placement in many schools resulted in an
increase in the variability of contextual factors (Wang, Reynolds, &
Walberg, 1990). The identification of the independent variable in studying
the effects of educating students with disabilities in inclusive settings
becomes a more complex issue, which is not satisfactorily resolved in most
special education research (Gallagher, 1990; Wang et al., 1990).