Examples and non-examples help pupils see the defining features and boundaries of a concept. The comparison is strongest when the pair differs in one important respect rather than several distracting ways.

Choose the decisive contrast

First identify what makes the concept what it is. Then select:

• a clear example;

• a closely matched non-example;

• one feature that explains the different classification.

For shape, compare a square with a rhombus that has unequal angles. For sentence structure, compare a complete sentence with the same wording missing a finite verb. In science, compare two materials that differ in the property used for classification.

Avoid trick examples that depend on an obscure exception rather than the intended learning.

Ask pupils to explain the boundary

Useful questions include:

• What is the same?

• What is different?

• Which difference changes the classification?

• What would need to change for the non-example to become an example?

• Can you create another example that looks different but still qualifies?

For example, when teaching prime numbers, compare 11 and 15. Ask pupils to use the number of factors, not appearance or size, to justify the difference.

Move from teacher selection to pupil generation

Begin with a carefully chosen pair. Then ask pupils to sort further cases, correct a non-example or create their own matched pair.

Check that pupils explain the underlying feature. Naming the category without justification does not show secure understanding.

Use comparison at the right point

Examples and non-examples are useful when introducing a boundary, spotting a misconception or revisiting a concept. They need not be added to every explanation.

Further guidance

• EEF: Cognitive science approaches in the classroom

• NCETM: The Five Big Ideas at Primary, Variation