Spaced repetition means reviewing something just as you are about to forget it, and leaving longer and longer gaps each time you remember it. It works because forgetting is normal, and because dragging a fading memory back into mind is what makes it last.
Many parents will recognise this. A child learns the year's fractions rules on Tuesday, scores well on the quiz on Thursday, and cannot do a single question in the exam six weeks later. Nobody was lazy. The memory simply faded, as memories do when nothing brings them back.
The forgetting curve, without the jargon
Memory fades fastest just after you learn something and more slowly afterwards. Think of a footpath across a field. Walk it once and the grass springs back within a day. Walk it again the next day and again a few days later, and soon there is a track that stays.
That is the whole idea. Each time you successfully bring something back from memory, the path gets a little clearer, so the next fade is slower and the next gap can be longer. Leave the field untouched for weeks and the path vanishes.
What the research says about gaps
The best-known evidence is a review by Cepeda and colleagues (2006), which pulled together 317 experiments on distributed practice, most of them on remembering word lists and facts rather than school exams. Two findings matter for parents. Spaced study led to better final-test performance than massed study, meaning cramming in one block. And the most effective gap was not fixed: it grew as the time until the test grew. If the exam is next week, short gaps are right; if it is in a term, longer gaps are better.
A separate review of study techniques (Dunlosky and colleagues, 2013) rated distributed practice as one of the two highest-utility techniques, alongside practice testing. In other words, the two habits that matter most are spreading revision out and testing yourself, and active recall handles the second half.
What a sensible schedule looks like
No one gap is magic, but for a Year 7 to 9 pupil, a shape like this is reasonable. Take a topic learnt on a Monday:
- Same day or next: a quick self-test, five minutes.
- About two days later: test again, focusing on what was missed.
- About a week later: again.
- About three weeks later: again, now closer to the exam.
Get it right with effort, and the gap stretches. Get it wrong, and the gap shrinks: the topic comes back in a day or two. That single rule, right means longer and wrong means sooner, is the heart of it. A simple calendar or planner can run this by hand, marking each topic with its next review date.
Do not feel bound to my numbers. They are an illustration of the shape, not a prescription, and a busy week that shifts a review by a day does no harm. What does harm is never coming back at all.
- Same or next day1Quick self-testFive minutes
- ~2 days later2Test againFocus on what was missed
- ~1 week later3Again
- ~3 weeks later4Again, nearer the exam
An illustration of the shape, not a prescription.
Where flashcards come in
Flashcards are popular because they hide the scheduling. Each card carries its own date, and the app only shows you what is due. This saves parents and pupils from running a complicated diary.
In Heddy, the review room works this way. After you flip a card you tap Again, Good or Easy, and each button shows the actual interval it would give, so the schedule is never a mystery. Again brings the card back soon; Good and Easy push it further out. Two details are tuned for school rather than for adults: a fixed twenty cards a day, so a tired 13-year-old can finish, and a ninety-day cap on the gap, so nothing drifts beyond a term. The grading buttons are explained in Again, Good, Easy.
- 1Try to recall
- 2Right, with effortThe gap stretches
- 3WrongIt comes back sooner
Common mistakes
- Grading yourself kindly. Marking a half-remembered card as easy sends it away for weeks. Be honest; "again" is not a failure, it is the system working.
- Spacing without testing. Looking at notes on day 1, 3 and 7 is better than once, but attempting recall each time is better still.
- Bunching it all into the last week. Spacing needs weeks. See revision without cramming the week before for a rescue plan if you are already late.
- Giving up after a bad review. Forgetting between reviews is expected, and it is exactly what the schedule is designed around.
For how to fit this into a full routine, try how to revise for KS3 exams.
Updated 30 Sep 2026. Written by Duke Harewood, who builds the tutors at aitutors.me.
Questions people ask
What is spaced repetition?
It means revisiting something several times, with gaps that get longer each time you remember it, instead of studying it all at once. A topic you get right waits longer to come back; one you get wrong comes back sooner.
What is the forgetting curve?
It is the observation that memories fade fastest soon after learning and more slowly afterwards, unless they are revisited. Each well-timed review tends to make the next fade slower.
Is spaced repetition just for flashcards?
No. It applies to anything you need to remember: maths methods, vocabulary, dates, equations. Flashcards simply make the schedule easy to follow. A planner that brings each topic back after a few days and then after a week works too.
How many days apart should reviews be?
There is no single correct gap. Research finds the best gap grows with how long you need to remember. For a school exam weeks away, roughly a couple of days, then about a week, then a few weeks is a sensible shape.