“An individual’s ability to learn, without reference to specific instruction or prior knowledge. Aptitude is most often measured by standardized tests (for example the Wechsler Intelligence Scale for Children [WISC]) or cognitive batteries of tests that also include achievement components (such as the Woodcock-Johnson). Other important aptitude tests include the Scholastic Aptitude Test and the American College Test, each of which plays a prominent role in college admissions.
Determining whether someone has a learning disability is generally based on a discrepancy between achievement and aptitude, as measured by standardized tests. Consequently, tests of aptitude such as the WISC and the Woodcock-Johnson play a central role in determining who is eligible to receive special education services.”
Excerpted from: Turkington, Carol, and Joseph R. Harris, PhD. The Encyclopedia of Learning Disabilities. New York: Facts on File, 2006.