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The principle of IDEA that states that a student with a disability must be educated with students without disabilities to the maximum extent appropriate for the student is the Least Restrictive Environment.
First, the meaning of IDEA. It stands for Individuals with Disabilities Education Act.
Federal Law in the United States requires that students with disabilities can study in a normal school environment with other non-disabled students to have the most natural and appropriate environment in the school premises. It is believed that the more time these students pass with non-disabled students, the better for them. This way they are going to feel they can study and work in a normal school environment.