The IQ- achievement discrepancy model is the traditional method used to determine if a student has a learning disability and needs special education services. The discrepancy model is based on the concept of the normal curve (bell curve). The discrepancy model assesses whether a substantial difference or discrepancy model exists between a student’s scores on an individualized test of general intelligent and his or her scores obtained for one or more areas of academic achievement. The accepted criteria to identify a student as having a learning disability using the IQ- achievement discrepancy is a difference of at least two standard deviations. The IQ-achievement discrepancy refers a student to a school psychologist. The system rarely identifies students with disabilities in early grades causing these children to struggle for years. Assessments do not always discriminate between disabilities and the results of adequate/effective teaching. The assessment does not inform instruction and typically students must fail first leading many students not to meet the discrepancy criteria but would still benefit. The procedure is a one-time assessment and is relatively easy to employ. A teacher does not have to spend a great amount of time in the identification process because a certified diagnostician conducts the IQ and achievement tests.
Why does the US Department of Education now recommends that schools use the RTI (“Response to Intervention” or “Response to Instruction”) Model rather than the Discrepancy Model to identify children with specific learning disabilities?
RTI is a lot more in-depth and specific to education and the student’s goals/objectives. It is an alternative to the IQ-achievement discrepancy model in some states (Idaho requires both RTI and IQ-achievement discrepancy) and is a multi-level prevention assessment and instructional data-based decision model for assessing effectiveness of intensive and individualized EBPs. It attempts to minimize the number of students referred to special ed by ruling out ineffective instruction as a reason. There must be data collected over 6 weeks.
Idaho
In Idaho, teachers must use both IQ-achievement and RTI. This allows for more students to qualify for services under the category of specific learning disability.