Interleaving means mixing different types of question in one session instead of repeating a single type twenty times. It feels harder, and that is the point: mixed questions make you choose the method, which is exactly what a maths exam asks you to do.
If your child's maths homework is ten questions that all use the same trick, they are practising doing a method. Exam papers don't announce the method. Mixed practice is how you rehearse choosing it.
Blocked versus interleaved, in one picture
Imagine a page of twelve questions.
- Blocked: twelve questions on adding fractions. By question three, the method is obvious. You stop reading the question properly and just run the routine.
- Interleaved: a fraction, then an angle, then a ratio, then an equation, then another fraction, and so on. Every question, you must first ask: what kind of problem is this?
Teachers and researchers talk about interleaving as a way of forcing that discrimination between problem types. Dunlosky and colleagues' 2013 review rated interleaved practice as moderate utility: promising, but with limited evidence, and in one study on fractions interleaving did not help. So treat mixed practice as a sensible habit rather than a proven rule. In the study they describe on volumes of solids, blocked practice scored better during practice but interleaved practice scored much better on a test a week later. Separately, the EEF's guidance on maths in Key Stages 2 and 3 stresses quick recall of number facts, which fits the flashcard advice at the end.
Why it feels worse and may work better
In blocked practice, your scores go up quickly and you feel clever. In mixed practice, you get more wrong at the start and feel slower. Children sometimes conclude the mixed set is "bad" or "too hard".
The difficulty is useful. Each question makes you pull the right method from memory rather than keeping it warm on the desk. It also means you return to older topics before you forget them, so mixed sets are doing two jobs: choosing and reviewing.
A parent line that helps: "If it felt a bit hard, that's the practice working. If every question felt easy, we mixed in too few things."
When to use blocks first
Do not throw a brand-new method into a mixed set. When your child is learning, say, solving two-step equations for the first time, a short block of five to six similar questions builds the basic routine. Once they can do those without looking at the worked example, move them into a mix that includes the new topic and two or three older ones.
In Heddy, this is roughly how a session runs: the tutor helps you through one problem at a time without handing over the answer, and the top rung of the hint ladder is a worked similar problem, then "now redo yours". Use that stage for learning and the mixed set for afterwards. See the hint ladder.
A sample mixed set for Year 8
Here is a set of eight questions you could use as a fifteen-minute mix. Adapt the numbers; the important thing is the variety of types.
- Simplify 3a + 5b − a + 2b. (algebra, collecting terms)
- Find the missing angle in a triangle with angles 47° and 68°. (angles)
- Write 18 : 24 in its simplest form. (ratio)
- What is 3/4 + 1/6? (fractions)
- Solve 4x − 7 = 21. (equations)
- A pack of 6 pens costs £3.90. What do 10 pens cost? (proportion)
- Find 15% of £80. (percentages)
- Find the area of a rectangle 7.5 cm by 4 cm. (area)
Rules for using it:
- Do them in a shuffled order, not topic by topic.
- Attempt each one before looking anything up. If stuck, mark it and move on; come back at the end.
- Afterwards, tick, then label each wrong one with the method it needed. That label is the real learning.
- Next week, swap some topics out and add two that they got wrong, so the set keeps changing.
A worked example of a label: if question 6 went wrong because the child divided the wrong way, write "proportion: find the cost of one first". Next time, that sentence is the hint.
- 1Shuffle the orderNot topic by topic
- 2Try each oneStuck? Mark it and move on
- 3Tick the answers
- 4Label each wrong oneWrite the method it needed
How often, and for how long
Mixed practice needs no separate evening. Ten to fifteen minutes, two or three times a week, is a reasonable start (my suggestion, not a researched dose). Put it at the end of a homework session or use it as a warm-up. Include one or two questions from last term so they never fully drop out of reach.
If you pair this with flashcards for the facts (times tables, angle rules, formulae), the facts stay quick, and the mixed sets are for deciding when to use them. See spaced repetition explained for parents for the flashcard half of that routine, and active recall for 11 to 14-year-olds for why trying before checking matters.
Questions people ask
What is interleaved practice in maths?
Mixing different types of question in one session, instead of doing twenty of the same type in a row. A child might do one fraction question, one ratio question, one angle question, then come back to fractions.
Why does mixed practice feel harder?
Because each question makes you first decide which method applies, not just carry one out. In blocked practice the method is given away by the page. That extra decision is the difficulty, and it is also what the exam will ask of you.
Should a child stop blocked practice entirely?
No. When a method is brand new, a short block of similar questions builds first confidence. Move to mixed questions once the method stops feeling shaky.
How often should we do a mixed set?
Little and often: ten to fifteen minutes, two or three times a week, is a realistic start. Include a few questions from older topics so they keep returning.