The law does not require your child's IEP to include educational methodology.
The position of the U.S. Department of Education is that including methodology in a child's IEP is an IEP team decision.
If the IEP team decides that your child needs a specific method to receive a free, appropriate public education, the instructional method may be included in the IEP.
In light of the legislative history and case law, it is clear that in developing an individualized education there are circumstances in which the particular teaching methodology that will be used is an integral part of what is 'individualized' about a student's education and, in those circumstances will need to be discussed at the IEP meeting and incorporated into the student's IEP.
Teachers must have the content knowledge and skills to teach children with disabilities. This includes the use of research based instructional practices and programs.
If a parent can request a specific program, and it is written into the IEP, the school has to provide it.