Tier 3 is the most intense level of intervention provided to students in general education. A student who does not respond to these intense interventions MAY qualify for special education services when it has been demonstrated that either the intensity or type of intervention required to improve student performance either exceeds the resources in general education or are not available in general education settings. Tier 3 in the conceptual model advocated by NASDSE and many other professionals is INTENSIVE INSTRUCTION, which may or may not include special education services. If Tier 3 is defined exclusively as special education, it is possible that additional intensive instructional programs would be set up OUTSIDE of the triangle model, which defeats the purpose of having the model for delivering services to all students.

Bill East, Director, National Association of State Directors of Special Education NASDSE, Myths About Response to Intervention (RtI), May 2006