Your child does not need both a 504 plan and an IEP (Individualized Education Program). If your child has an IEP, any 504 accommodations are included in the IEP.
An IEP is the document created under IDEA (Individuals with disabilities education act) to provide individualized education instruction to meet a child’s specific needs. IDEA and an IEP have more rights and protections built into the law than a 504 plan does. As an IEP is more encompassing, it pulls into it any 504 accommodations to become part of the IEP. Many IEP’s will have pages listing these accommodation, like preferential seating, extended time on tests, extra sets of books, and the ability to turn in homework late are just a few of the most popular one.
A 504 plan stems from section 504 of the 1973 Rehabilitation act. The easiest way to think about it section 504 does for education what the American with disabilities act does in the workplace. it requires the schools to grant reasonable accommodations due to the child’s disability. What child needs will depend on the condition. Generally, individual education services are not provided under a 504 plan. That does not mean that no services can be provided with just a 504 plan. A 504 plan can still require a teacher to notify a parent of any missing homework for the week, could still give the child access to a resource room as a quiet place to complete assignments or tests, and can still require a school to read a test to a student.
What an IEP does that a 504 plan cannot is offer services to address specific educational needs of the child. A 504 plan cannot modify the child’s curriculum (or grading scale), but an IEP will. A 504 plan will not give a child access to special education services like speech therapy, occupational therapy, or physical therapy. These services are part of special education. They are individualized programs to address the specific needs of the child. Think of it this way, if not every child in the school can be in the program, then it likely falls under special education and requires an IEP. On a side note, some states apply this to gifted children as well and write IEP’s for them. Not all states treat gifted children under IDEA) and the child needs an IEP, for a list of how states treat gifted kids and IEPs see Hoagies Gifted Education. This is a great resource for parents of gifted kids and those of us with 2-e (twice exceptional: gifted children with disabilities) kids.
On a practical side, the enforcement of an IEP is much more parent friendly then a 504 plan. The entire process of enforcement is outlined in IDEA and includes administrative remedies before the parents must pursue the school in federal court. On the other hand, the only option to enforce a 504 plan is to head straight to federal court.