The IDEA (Individuals with Disabilities Education Act) pretty carefully lays out the ground rules for a special education assessment. Among the various regulations related to administering a case study evaluation are that assessments “are used for the purposes for which the assessments or measures are valid and reliable; are administered by trained and knowledgeable personnel; and are administered in accordance with any instructions provided by the producer of the assessments.” We bring this up because the fifth edition of the Wechsler Intelligence Scale for Children (WISC), one of the mainstays of cognitive testing for children, was released this past fall. So does the existence of a newer edition of such a standard battery render the previous edition of the WISC no longer valid? It’s a good question, because not even professional psychological organizations appear to agree on at what point a previous edition of an exam becomes obsolete. Moreover, as a practice point, we have won cases based on the fact the district knowingly or carelessly made decisions based on outmoded test instruments.