Why number bonds matter

A number bond is a pair (sometimes a trio) of numbers that combine to make a target number.

The bonds to 10 are: 0+10, 1+9, 2+8, 3+7, 4+6, 5+5, 6+4, 7+3, 8+2, 9+1, 10+0. Eleven pairs (or six, if you ignore order).

The bonds to 20 double the count, and add a layer of difficulty: some require bridging through 10 (8+5 = 8+2+3) which is a meaningfully harder mental skill than the bonds to 10.

The bonds to 100 in tens (10+90, 20+80, etc.) and the bonds within 100 are KS2 territory.

A child who has "fluent recall" of a bond can answer it in under two seconds without working it out. That speed is the difference between fluency and competence, and it matters far more than people realise.

Cognitive psychologists describe working memory as a small, fragile resource. When a child does mental arithmetic, every operation that isn't automatic eats into that resource.

A child who hasn't internalised 7+3 = 10 will, when faced with 27+13, spend their working memory on the small sum rather than on the structure of the bigger one. The arithmetic isn't wrong: it's just slow and exhausting. By the time they're doing Year 5 multi-step word problems, the cognitive load of the basic sums has crowded out the actual reasoning the question is asking for.

This is the mechanism by which children "fall behind" in maths. It's not that they can't do it. It's that they can't do it fast enough to free up the headspace to do the next thing.

The National Curriculum for England is explicit:

• – End of Year 1: pupils should "represent and use number bonds and related subtraction facts within 20"
• – End of Year 2: pupils should "recall and use addition and subtraction facts to 20 fluently, and derive and use related facts up to 100"

The DfE's Ready to Progress criteria for Key Stage 1 mathematics reinforce this. Fluent recall of these facts is treated as a non-negotiable foundation, not an aspirational target. A child who leaves KS1 without it is flagged for catch-up.

In practice, this means: by the start of Year 3, fluent recall of bonds to 20 is the assumed baseline for everything that follows.

Number bonds are typically taught through three mechanisms: chanting, worksheets, and short-burst games like flashcards. All three work, for some children.

The children for whom they don't work tend to share a profile. They're not failing the worksheet: they're slowly working out each sum rather than recalling it. The teacher sees the right answers on the page and moves on. The gap doesn't show up until it's too late to easily fix.

What's been missing is a way to measure recall speed, not just accuracy, and to adapt the practice so each child drills the bonds they're still working out, not the ones they already know.

Number bonds are most useful when they become automatic. Animal Bonds is built around repeated practice with the game adapting to where each child is. The aim is fluency: answering quickly and correctly, consistently. It addresses the gap in three specific ways:

1. 1

   Speed matters as much as accuracy. Every question in the game has a soft timer; the adaptive engine treats slow correct answers as "not yet fluent" and re-introduces them.

2. 2

   Practice should be differentiated to the individual fact, not the individual child. A child can be fluent on bonds to 10 but failing bridging-through-10 cases. The engine tracks every fact separately and drills accordingly.

3. 3

   Children need to want to practise. The game wrapper (animals, races, biomes, cosmetic unlocks) exists because intrinsic motivation works and external nagging doesn't.

The result is a tool that does what classroom drilling can't: gives every child exactly the practice they need, at the speed they need, with the data to prove it's working.