IQ Tests for Children: Which Test, What Age, and What the Score Means

If your child is under six, the single most useful thing on this page is that waiting is usually the right answer. Scores at that age are real measurements of something, but they are unstable enough that they predict the same child’s score a few years later only loosely.

Which test your child would take

Children are not given adult tests scaled down. There are separate instruments with their own norming samples, and which one a child sits depends almost entirely on their age.

The WISC-V is the one most parents encounter. It covers ages 6 years 0 months to 16 years 11 months and is the standard instrument for school psychologists across the English-speaking world.

There is a deliberate overlap between the WPPSI-IV and the WISC-V, from 6 years 0 months to 7 years 7 months, and the choice within that window matters. A child of average or higher ability is usually given the WISC-V. A child with suspected developmental delays is usually given the WPPSI-IV, because it has an easier floor and can therefore distinguish between levels of difficulty that the WISC-V would simply record as “low”. If your child is in that age band, it is reasonable to ask the assessor which they have chosen and why.

At what age does a score become meaningful?

This is the question worth getting right, and there is now a clear answer to it.

A 2024 meta-analysis by Breit and colleagues examined how stable cognitive test scores are across childhood. The finding that matters for parents: the level of test-retest stability normally required before a score can carry an individual diagnostic decision, a correlation of about .80 or higher, is only reached after around age seven, and even then only across relatively short intervals between tests.

Below about six, scores are genuinely variable. A child can test at 118 at four and 104 at eight without anything having gone wrong, and without either number being an error. Young children’s performance is affected by attention span, mood, familiarity with the examiner, language development and simple developmental timing, all of which change enormously over a couple of years.

From school age onward the picture improves considerably, and by adolescence scores are about as stable as adult scores, which is to say quite stable. The broader pattern across a whole lifetime is covered in our guide to how IQ changes with age.

The practical rule most specialists give: wait until at least six, preferably seven or older, unless there is a specific reason not to. Good reasons to test earlier include a suspected developmental delay, a specific concern a clinician wants to investigate, or a school placement process with its own deadline. Curiosity is not one.

How school gifted screening actually works

Worth knowing, because the process is often less thorough than parents assume and understanding it tells you what a result is worth.

Most initial screening uses group-administered ability tests. A whole year group sits the same paper at the same time. These are cheap and fast, which is why they are used, and noticeably less reliable than individual assessment: a child who is tired, distracted, unwell or simply not engaged that morning can be missed entirely.

Children flagged by screening are usually then referred for an individually administered test, typically the WISC-V, given one-to-one by a psychologist who can observe how the child works rather than just marking answers. This is the assessment that actually carries weight.

Most modern frameworks also combine the score with achievement data, teacher ratings and portfolio evidence rather than using a single threshold. Cut-offs vary widely between authorities, commonly somewhere between 120 and 135, which means a child identified as gifted in one district might not be in the next one over. That variation is covered in our guide to an IQ of 130.

Should you pay for private testing?

Sometimes clearly yes, often no, and the deciding factor is what you intend to do with the result.

Reasonable grounds for private assessment:

• The school will not test, or has a long waiting list, and there is a placement or appeal with a deadline.
• You suspect a learning difficulty alongside high ability. A full individual assessment can show an uneven profile that a single composite score would hide entirely, which is often the key to getting appropriate support.
• A clinician has recommended it as part of investigating a specific concern.

Weaker grounds:

• Wanting to know the number. It is expensive, it is unstable if the child is young, and in most cases it does not change what you would do next.
• Hoping a high score will unlock something. Schools generally run their own assessments and are not obliged to act on a privately obtained one.

If you do go privately, ask which instrument will be used, whether you will receive the index scores rather than just the Full Scale figure, and whether the report includes confidence intervals. All three should be yes, and the index breakdown is usually the most useful part of the document.

What a child’s score does and doesn’t tell you

Three things it genuinely tells you:

• Where they sit relative to other children their age on reasoning tasks, which is useful for matching schooling to ability.
• Whether their profile is even or uneven. A child strong in verbal reasoning and weak in processing speed has different needs from one who is flat across the board, even at the same composite.
• Whether something warrants further investigation. A markedly uneven profile is often the first documented sign of a specific learning difficulty.

And three it does not:

• How the child will turn out. Childhood scores predict adult outcomes loosely at best, and the most famous longitudinal study of high-scoring children produced no Nobel laureates while missing two future ones it screened and rejected.
• Anything about character. Persistence, curiosity, kindness and resilience are not measured and do not come bundled with a high score.
• A precise ranking. Every score carries a standard error of roughly 3 to 5 points. A 128 and a 133 are not meaningfully different results.

One practical note on talking to your child about it. The number is information about how they performed on a set of puzzles, not a verdict on who they are, and children handle it best when it is framed that way. A score is far less interesting to most children than adults expect, and far more loaded if the adults treat it as a headline.

Online tests and children

Direct about this: online IQ tests are not appropriate for children, including ours.

They are not normed on children, which means the comparison group is wrong and the resulting number does not mean what it appears to. They are unsupervised, so there is no way to know whether the child was helped, distracted or guessing. And no school, psychologist or gifted programme will accept one as evidence of anything.

Our own assessment is built and normed for ages 16 and above. If your teenager is 16 or older it is a reasonable way to get an indicative score. Below that, it will produce a number that does not mean what it says.

Frequently asked questions

The bottom line

Which test depends on age: the WPPSI-IV up to about seven and a half, the WISC-V from six to sixteen, the adult scales from sixteen. Whether to test at all depends on what you would do with the answer, and whether to test yet depends on how old your child is. Stability sufficient to hang a decision on does not arrive until around age seven.

If there is a specific concern, a placement process or a suspected learning difficulty, a proper individual assessment is worth doing and the index breakdown will tell you more than the headline number. If it is curiosity, waiting costs nothing and testing early risks attaching weight to a figure that will not hold.