IQ testing for children uses a standardized IQ test to measure a child's cognitive abilities, such as verbal understanding, reasoning, problem solving, working memory, and processing speed. IQ stands for "intelligence quotient." Results are reported on a scale where 100 is average and most children score between 85 and 115. The test is individually administered by a psychologist, most often as part of a special education evaluation or for gifted identification.
What does an IQ test measure?
Modern IQ tests measure a range of cognitive skills, not one single ability. Depending on the test, these may include:
- Verbal reasoning: vocabulary, word knowledge, and understanding concepts
- Visual-spatial skills: seeing patterns and putting shapes together
- Fluid reasoning: solving new problems and finding rules or patterns
- Working memory: holding and using information for a short time (see working memory)
- Processing speed: how quickly and accurately a person can do simple tasks
An IQ test does not measure creativity, motivation, character, social skills, or talents in areas like art and music. It also does not measure what a child has learned in school. That is the job of achievement tests, which cover reading, writing, and math.
Common IQ tests for children
An IQ test used in a school evaluation is administered one-on-one by a trained professional, usually a school psychologist, and often takes one to two hours. The most common tests include:
- Wechsler Intelligence Scale for Children (WISC-V): the fifth edition of the WISC, used for children about ages 6 to 16. It gives a Full Scale IQ and index scores for Verbal Comprehension, Visual Spatial, Fluid Reasoning, Working Memory, and Processing Speed.
- Wechsler Preschool and Primary Scale of Intelligence (WPPSI-IV): a version for young children, from about age 2½ to 7.
- Stanford-Binet Intelligence Scales, Fifth Edition (SB5): one of the oldest IQ tests, updated over many years. It can be used from early childhood through adulthood.
- Other tests: such as the Woodcock-Johnson Tests of Cognitive Abilities, the Kaufman Assessment Battery for Children, and nonverbal tests for children with limited English or language disorders.
Online IQ tests are not the same as these standardized tests. They are not given by a trained examiner, are not normed on a representative group, and cannot be used for school decisions.
The IQ scale and score ranges
Most IQ tests use a standard score scale with an average IQ of 100 and a standard deviation of 15. The standard deviation shows how spread out scores are. About 68% of people score within one standard deviation of the mean (85 to 115), and about 95% score within two standard deviations (70 to 130).
Test publishers use slightly different labels, but a typical IQ score range looks like this:
- 130 and above: very superior or extremely high
- 120 to 129: superior or very high
- 110 to 119: high average
- 90 to 109: average
- 80 to 89: low average
- 70 to 79: borderline or very low
- 69 and below: extremely low
Every score has some measurement error, so reports often give a confidence interval, such as "95 to 105," instead of a single number. Percentile ranks are also common. A percentile of 50 means the child scored as well as or better than half of children the same age.
IQ testing in special education evaluations
Under the Individuals with Disabilities Education Act (IDEA), a school must evaluate a child in all areas of suspected disability before deciding on special education. The law says the team may not use any single measure or assessment as the sole basis for deciding eligibility (34 CFR 300.304). An IQ test is often one tool among many, along with achievement testing, observations, and input from parents and teachers. The school must get parent consent before the initial evaluation.
Intellectual disability
IQ testing plays a central role in identifying an intellectual disability. The IDEA defines it as significantly subaverage general intellectual functioning, existing at the same time as deficits in adaptive behavior, that appears during the developmental period and adversely affects educational performance. In practice, "significantly subaverage" usually means an IQ about two standard deviations below the mean, or roughly 70 or below, but states set their own criteria. An IQ score alone is never enough; the team must also look at adaptive skills such as communication, self-care, and social skills.
The old discrepancy model and SLD today
For many years, schools identified a specific learning disability by looking for a "severe discrepancy" between a child's IQ and their achievement scores. Critics said this "wait to fail" model delayed help until the gap was large. Since the 2004 reauthorization of the IDEA, federal rules (34 CFR 300.307) say states may not require the discrepancy model. States must allow a process based on the child's response to scientific, research-based intervention, such as RTI or MTSS, and may allow other research-based methods, such as looking at patterns of strengths and weaknesses. Some states still permit the discrepancy approach, so the process varies by state.
IQ scores can also help the team understand the learning profile of a student with ADHD, autism, or a brain injury and inform educational planning.
IQ testing and gifted programs
Many school districts also use an IQ test or other intelligence test for gifted testing. A high score, often around 130 or above, may be one factor for a gifted and talented program, but criteria vary by district and state. Gifted education is not covered by the IDEA, so each state sets its own rules. Some children are both intellectually gifted and have a disability, such as a learning disability, ADHD, or autism. These students are often called "twice-exceptional." For them, the full cognitive profile of strengths and weaknesses matters more than one number.
Limits and bias of IQ tests
IQ tests are useful, but they have real limits:
- A score is a snapshot of one day. Anxiety, illness, fatigue, or attention problems can lower results.
- Language, culture, and life experience can affect scores, especially on verbal tasks. The IDEA requires that assessments be selected and given so they do not discriminate on a racial or cultural basis and be given in the child's native language when feasible.
- Disabilities in vision, hearing, motor skills, or speech can hide what a child really knows unless the test is adapted or a nonverbal test is used.
- The Full Scale IQ can be misleading when index scores are very uneven. The pattern of strengths and weaknesses is often more helpful than the overall number.
Concerns about bias have a long history. In the Larry P. v. Riles case, a federal court in California restricted the use of IQ tests to place Black students in classes for students with intellectual disabilities. The case is one reason schools now use multiple measures.
What parents should ask about IQ testing
- Which tests will be used, and why were they chosen for my child?
- Who will give the test, and what are their qualifications?
- Was the test given in my child's strongest language and in a way that fits any disability?
- What do the index scores show, not just the overall score?
- How do these results connect to my child's learning needs and the IEP?
- Can I get a copy of the report before the meeting?
If you disagree with the school's evaluation, you have the right to ask for an independent educational evaluation at public expense, as described in your procedural safeguards. Testing is also repeated or reviewed during a reevaluation, at least once every three years unless the parent and school agree it is not needed.
Frequently asked questions about IQ testing for children
How do I get my child's IQ tested?
If you suspect a disability, you can ask your child's public school in writing for a free evaluation under the IDEA's Child Find duty. You can also pay a private licensed psychologist, who will administer the test and give you a written report.
What is an average IQ score?
The average IQ is 100 at every age, because each child is compared with others the same age. So the average score for a 7-year-old is also 100. Scores from about 90 to 109 are usually described as average.
At what age can a child take an IQ test?
Some tests, such as the WPPSI-IV and the Stanford-Binet, can be used with children as young as 2 or 3. Scores are generally more stable once children reach school age.
Does a low IQ score mean my child qualifies for special education?
Not by itself. Eligibility under the IDEA depends on meeting the criteria for a disability category and needing specially designed instruction. The team must use many sources of information, not a single score.
