This is not actually part of IDEA, but rather a portion of the federal civil rights statutes called the Rehabilitation Act of 1973. It is the section that applies to the education of physically disabled students and adults in the US, and will only be accessed through your school district’s special services department because it has no other home. Every district in every state is required to have a 504 officer, whose job it is to make sure that every student covered by Section 504 of the Rehabilitation Act is getting what he or she needs in the way of appropriate education.
Most often, Section 504 is used as a temporary fix for students who are ill or have been injured severely enough to be unable to follow their normal daily routines, so it is not, per se, special education. Students with Attention Deficit Disorder fall into the 504 category, as do students with chronic illnesses. A student’s 504 plan might include alterations to attendance policies to allow for doctor’s appointments or physical therapy. It might include a shortened school day. It might even include homebound instruction if the student is unable to travel to school.
What is does not necessarily include is a specially modified curriculum in a given subject area. If the student has had major surgery to his arm, for instance, he might be allowed to tape record his lessons or have someone act as a scribe to write his homework or tests. He will still, however, be responsible for the curriculum that is being covered. Special Education allows for curriculum modifications.