The Key Concepts of IDEA (1997 and 2004) are:
Zero Reject. A free appropriate public education is available to all children with disabilities, residing in the State between the ages of 3 and 21, inclusive, including children with disabilities who have been suspended or expelled from school. In IDEA 2004, such a free appropriate public education emphasizes "special education and related services designed to meet their unique needs and prepare them for further education, employment, and independent living."
Non-discriminatory evaluation. Determine whether the student has a disability and, if so, what needs the student has for special education and related services. In IDEA 2004 provisions are made for alternative assessments. There are also provisions to prevent the over-representation of children from minority groups in special education.
Appropriate education: Develop and implement an Individual Education Program (IEP). The 1997 amendments included an increased emphasis on participation of children with disabilities in the general curriculum and the involvement of regular education teachers in developing, reviewing and revising the IEP. IDEA 2004 continues this emphasis with significant changes to the process. IDEA 2004 also adds an emphasis on preparing young people for post-secondary/further education, and on improving the child's academic achievement and functional performance while in school. Transition plans are required at age 16 rather than age 14 under IDEA 1997.

Photo courtesy Ann Marsden
Least restrictive environment: Educate a student with a disability, to the maximum extent appropriate for the student, with students who do not have disabilities. in IDEA 2004, this was expressed as follows – To the maximum extent appropriate, children with disabilities, including children in public or private institutions or other care facilities, are educated with children who are not disabled, and special classes, separate schooling, or other removal of children with disabilities from the general educational environment occurs only when the nature or severity of the disability of a child is such that education in general classes with the use of supplementary aids and services cannot be achieved satisfactorily.
Procedural due process: Procedures that schools and parents have at their disposal to hold each other accountable. The 1997 and 2004 amendments make mediation available as a means for more easily resolving parent-school differences.
Parent participation: The 1997 and 2004 amendments enhance parent participation in eligibility and placement decisions. In IDEA 2004, schools must obtain informed parental consent before providing special education and related services. If parents refuse, the school district may not use procedures such as mediation and due process in order to provide services.
Outcomes and Standards: The 1997 amendments required states to include students with disabilities in state and district-wide testing programs (with appropriate accommodations when necessary); and establish performance goals and indicators for students with disabilities. The 2004 amendments place an increased emphasis on academic achievement and functional performance. The 2004 amendments are coordinated with the No Child Left Behind Act.
The 1997 IDEA called for major re-orientations in programs. Gartner, for instance, compared programs in the New York City Public School before and after the 1997 Amendments.