In most American public schools today, IQ tests (in conjunction with achievement tests, which are described below are primarily used to determine whether a particular child needs supplemental educational programming or services above and beyond a traditional classroom. Unlike hearing or vision screenings or tests of children's physical health, IQ tests are generally voluntary in nature and not mandatory. Not all children receive them. There are no specific laws, requirements or guidelines suggesting that all children must be administered intelligence tests at specific ages.
The two primary reasons children are asked to receive IQ testing have to do with the school's efforts to document special education needs. Children may be having difficulty mastering age appropriate tasks and the school (or parent) suspects that a learning disability, cognitive disability, intellectual disability, or developmental disorder may be present. Alternatively, children may be perceived as not adequately challenged by age appropriate tasks because they are "gifted", and correspondingly bored because their schoolwork is too easy. In this case, the school (or parents) may want to document the child's high IQ to qualify the child to attend gifted and talented classroom education programs. Some private schools may require students to take IQ tests as part of their admissions process. In this situation, these schools may have limited numbers of available spots for students and therefore require a certain minimum IQ score in order to be admitted. Please see our Special Education document for further information on these assessment processes.
Achievement Tests vs. Intelligence Tests
Intelligence tests (IQ tests) are usually administered with Achievement tests. Some people incorrectly assume that IQ tests and achievement tests are the same thing, and measure the same skills so it is worth while to distinguish them here. The key distinction is that intelligence tests are designed to assess a child's problem solving abilities and intellectual potential, while achievement tests are designed to measure children's actual performance; the knowledge a child has learned. Intelligence is an ability; a dynamic process, ideally independent of specific knowledge. In contrast, achievement measures more static content, such as might fill a database. Achievement tests can get at facts, and also at methods or procedures that a child may have learned, but they are not fundamentally aimed at assessing ability.
Achievement tests measure a child's knowledge about a certain topic, such as reading, writing, science, or citizenship. In the middle childhood years, these tests are used not only to gauge children's level of knowledge (i.e., whether children are performing academically at, below or above grade level), but also to measure a particular school's ability to teach children what they need to know.
Achievement tests are commonly administered to whole classes or groups of children simultaneously, while IQ tests are typically administered to an individual child. The gold standard IQ tests (the WAIS and the Stanford-Binet) require individual administration, as they depend on one-on-one interaction between a test administrator and a test subject. Periodic achievement testing of students is required by American federal law, and group test results for public school districts are monitored by state governments. As we mentioned above, there is no law requiring that children are administered an IQ test.
If all is going well developmentally, children's intelligence (IQ) test results and their achievement test results should agree, with measures of achievement roughly in line with measures of intelligence potential. Finds of discrepancy between the two types of tests may indicate the presence of a learning disorder or similar issue. Learning disorders (LINK to topic discussion in Children's Disorders) are typically suggested by a finding of relatively strong IQ scores coupled with relatively poor achievement scores. When this pattern is present, individual sub-tests within the IQ profile can be inspected to see if a distinctive pattern of strengths and weaknesses is present there, indicating the child's particular weakness involving verbal skills (suggesting a reading or writing disorder), or mathematical skills, etc..
Children identified as needing special education/accommodations for learning disabilities, or gifted services on the basis of testing will likely need to be re-tested periodically during the remainder of their academic career to allow for their education plans to be modified as their needs change. More information about Learning Disabilities can be found in our topic center on Child Mental Health Disorders and Illnesses, and our topic center on Learning Disorders. Information on Special Education services can be found in our Special Education document.