In Letter to Dr. Perry Zirkel, the Office of Special Education Programs (“OSEP”) responded to a series of three questions regarding the implementation of response to interventions (“RtI”) and multi-tiered systems of supports (“MTSS”). First, the letter clarified that the Individuals with Disabilities Education Act (“IDEA”) does not define RtI or MTSS. Second, the letter provided that IDEA Part B funds cannot be used to provide special education and related services during the secondary and tertiary levels of the framework if the child has not yet been evaluated and found to have a disability. Additionally, parents must provide consent for students to receive the initial provision of services. Third, and finally, the letter addressed if RtI can be used to implement least restrictive environment (“LRE”), as required under IDEA. The letter clarifies that there is nothing in IDEA to prevent students who qualify for special education from receiving RtI services, and that all special education services must conform with an eligible student’s IEP and related services to provide the student with a free appropriate public education (“FAPE”).