As an index of mental functioning, intelligence was thought to pervade all tasks performed by an individual and all of that individual's abilities. A number of researchers subsequently attempted to define intelligence as only one representation of an individual's abilities. Despite the attacks leveled at the approach, intelligence, as measured by tests, does correlate well with school grades and various achievement criteria. Alfred Binet was commissioned in 1904 by the Minister of Public Instruction in France to devise a method for detecting children who were "subnormal" in intellectual abilities so that they could be placed in special schools. The interpretation of verbal scores versus performance scores and of individual subtest scores has been attempted by many researchers. The Wide Range Achievement Test and the Peabody Individual Achievement Test are those that the health care professional is most likely to encounter.