What does “discrepancy” mean?
A: People often talk about “discrepancy” when they discuss learning disabilities.
Discrepancy refers to a difference between ability and achievement. A student with a learning disability may, in general terms, seem quite capable of learning but have unexpected difficulty in one or more of the academic areas. Originally, the concept of discrepancy was probably used to differentiate between students who had low achievement because of low ability (i.e., individuals with low ability or IQ) and those whose low achievement was unexpected (i.e., individuals with normal ability).
Although the federal definition does not direct them to do so, many schools require a numeric discrepancy between ability and achievement test scores for a student to be identified as having LD. Usually the discrepancy is based on a comparison of scores from standardized IQ and academic achievement tests. Sometimes schools use a formula to determine whether the discrepancy is large enough to qualify a student for LD services. Sometimes teams charged with determining eligibility consult a table with rows and columns that compares IQ and achievement (this amounts to a formula, too).
The concept of a discrepancy—unexpected underachievement—has been a part of learning disabilities throughout most of its history, but it became controversial in the 1990s. Some authorities in LD contend that, for example, there is no evidence of difference in the acquisition of reading skills between children with and without a discrepancy. They also argue that requiring a child to have a discrepancy works against giving special instructional services to very young children; if the services could be provided when they are young, then the problems might be prevented. DLD’s booklet on response to instruction, Thinking about Response to Intervention and Learning Disabilities: A Teacher’s Guided, discusses these issues.