---
title: "Teaching a Child to Check Their Work"
url: https://www.learningloftinstitute.com/answers/how-do-you-teach-a-child-to-check-their-work
source: Learning Loft Institute
language: en
updated: 2026-08-21
section: "Answers › Teaching a Child to Check Their Work"
---
# Teaching a Child to Check Their Work
> **Answer.** Name the check rather than asking for one. Rereading cannot find an error because it repeats the reasoning that produced it — the child sees what they meant, not what they wrote. A check only works if it computes something different: substitute the answer back, estimate before calculating, and ask whether the result is possible.
## Why rereading finds nothing
You reread with the same reading of the question and the same choice of method that produced the answer. If the error was in either — and most errors are — rereading reproduces it faithfully.
There is a second problem specific to your own working. A child reading their own lines sees the intention behind each one rather than the line itself. The 3 that should have been a 5 reads as a 5, because that is what was meant. This is why 'I did check it' is usually a true statement and a useless one.
## Check one: put the answer back in
This is the only check that is a proof rather than an opinion, and it runs the mathematics backwards, which is what makes it independent of the original method.
It is different from redoing the question. Redoing repeats the method and therefore repeats the error. Substituting reverses it.
- Solved 4x − 3 = 17 and got x = 5? Put 5 back: 4(5) − 3 = 17. It holds.
- Factorised x² + 7x + 12 as (x + 3)(x + 4)? Expand it. If it comes back to the original, it is right.
- Rearranged a formula? Put one set of numbers into both versions and see whether they agree.
- Solved simultaneous equations? Substitute into both equations, not only the one you used last.
- Found a missing angle or side? Put it into the diagram and check the totals still work.
## Check two: estimate before you calculate
The estimate goes at the top of the working, in brackets, before any calculation happens. Before 4,368 ÷ 24, write approximately 4,000 ÷ 25 = 160. If the calculator then produces 1.82 or 1,820, you know something is wrong before looking at a single digit of the answer.
This is the check that catches place-value and decimal-point errors, which are simultaneously the most common and the least visible. An answer that is ten times too large looks exactly as plausible as a correct one, and nothing about rereading it will reveal otherwise.
The order matters. An estimate written after the answer is contaminated by the answer — it drifts towards whatever number is already on the page. It has to be a genuine prediction to function as a test.
## Check three: could this be true?
Three seconds, no working, and it is the only check that functions on a question where the student has no idea whether the method was right.
- An angle of 250° inside a triangle.
- A probability of 1.4, or a negative one.
- A percentage decrease that made the number bigger.
- A person 0.17 m tall, a walk at 900 km/h, a monthly bill of PKR 4.
- A hypotenuse shorter than one of the other two sides.
- An average that lies outside the range of the data.
## Making it a routine rather than an instruction
'Check your work' names a goal and no action, which is why a child asked to check will reread — rereading is the only thing the phrase suggests. Naming which of the three checks to run is the whole difference between the instruction working and not working.
- The check is written down, not done in the head. If it is not on the page, it did not happen.
- Mark your child's work by writing 'check Q4' rather than a cross. They find the error; you do not supply it.
- Write 'check Q4' next to some answers that are right, or the phrase quietly becomes a synonym for 'this is wrong'.
- Give checking its own time: the last five minutes of a thirty-minute set, with the check named.
- Do it on homework every week rather than on tests only. A routine used twice a year is not a routine.
## What changes the answer
- Substituting back is available for equations, factorising and rearranging, and not for a single-step calculation, which needs the estimate instead.
- A child who is rushing will not check however well the check is taught, so the rushing has to be dealt with before the checking.
- On a calculator paper, re-entering the same keystrokes is not a check — it reproduces the original mistake perfectly.
- In an exam, checking competes with attempting; a student who has not finished the paper should be attempting, not checking.
## Questions
### My child says they checked it and it was still wrong. What now?
Ask which check they ran. Almost always the honest answer is that they read it again. Naming the check — substitute back, estimate, is this possible — turns a vague instruction into a specific action, and that alone changes the hit rate more than any amount of insisting.
### Should they use a calculator to check a non-calculator question?
For homework, yes — at the end, and after the estimate has been written. It tells them whether the method was right, which is the more valuable information. In the exam it is not available, which is precisely why the estimate is the habit worth building now.
### How long should checking take?
About a fifth of the time the questions took. Thirty minutes of work, five or six minutes of checking. Much longer than that and the student is redoing the set rather than testing it, which is slower and no more accurate — and it makes checking feel like a punishment for having done the work.
### Does this transfer to other subjects?
The estimate and the possibility check do, roughly — a date, a quantity or a conclusion can be sanity-checked the same way. Substituting back is specific to mathematics and is the strongest of the three, which is one good reason to teach the habit here first.
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