How to find gaps in your child's maths knowledge

By the BrightHop team · Published 24 October 2026 · Updated 24 October 2026

Short answer

Look for the question type your child gets wrong, then ask which earlier skill that question depends on. A gap is usually one missing prerequisite, such as knowing the pairs that make 10, not 'being bad at maths'. A short check made of questions from one topic, followed by a look at the kinds of mistakes, finds it faster than a long test or more worksheets.

Why maths gaps are hard to see

Maths skills build on each other. A child can often get through a topic by memorising a pattern, so the missing skill underneath only shows up later, in a different-looking question. A mark of 6 out of 10 tells you something went wrong, but not what.

A gap is a specific skill a child has not yet secured. See what a maths learning gap is for the definition.

Five steps to find the gap at home

Pick one topic that feels shaky, such as adding, subtracting or time. Do not try to test everything at once.
Ask a handful of questions in different forms. For addition that means 4 + 3 = ?, then 4 + ? = 7, then a short story problem.
Note which form breaks. If 4 + 3 is fine but 4 + ? = 7 is not, the child knows the calculation but not yet the relationship between the parts and the total.
Ask the child to explain how they got the answer. 'I just added the numbers I could see' is a different gap from 'I counted and lost my place'.
Work out the prerequisite. Ask what a child must already know to answer the question that went wrong, and test that skill next.

Example: the same skill in three forms

Year 1 addition, three ways of asking

4 + 3 = ? (join two parts: the total is unknown)
4 + ? = 7 (the total is known, a part is missing)
? + 3 = 7 (the first part is missing)

A child who is confident with the first form but not the others usually has the 'two parts make a whole' idea only in one direction. The fix is to teach the relationship, not to give more of the first form. See why a child can add but struggles with missing-number questions.

How to know it is a real gap

The same kind of question goes wrong more than once, across different days.
The wrong answers follow a pattern, such as always adding the two numbers shown.
The child can do an easier version of the same skill, but not the next one up.
A single slip, such as a misread number, does not repeat when the question is asked again. That is a careless mistake, not a gap.

What to do once you have found it

Teach the one missing skill, in a few minutes with a worked example and a picture or objects, then re-ask a fresh question to see whether it stuck. Then move to the next skill. How to know what maths skill to teach next covers the order.

Try it

Not sure whether addition is where the gap is? The free addition Skill Check asks five short questions, including the missing-number form, in about three minutes. No account needed.

Try the free addition Skill Check

Frequently asked questions

How many questions do I need to ask to find a gap?

Five to ten well-chosen questions from one topic is usually enough to see a pattern. More questions help only if they are different in form, not repeats of the same question.

Should I use my child's school report to find gaps?

A report shows where a child sits against expectations, which is useful context. It rarely names the specific missing skill, so use it to choose a topic and then check that topic directly.

Sources

Australian Curriculum v9: Mathematics, Year 1 (ACARA)
Australian Curriculum v9: Mathematics, Year 2 (ACARA)
Inside the Black Box: Raising Standards Through Classroom Assessment (Black & Wiliam, Phi Delta Kappan, 1998)

This guide is written by the BrightHop team from BrightHop’s own teaching approach. It is not independent research and not official curriculum guidance. Curriculum and research statements link to their original sources above. Skill Checks are informal and do not replace a teacher’s advice. About BrightHop