Science // Scientific Inquiry

Fair testing

Set up simple practical enquiries, comparative tests, and fair tests, understanding the importance of changing only one variable at a time

Ages
7 to 9
Type
Method
Builds on
1 topic
Leads to
2 topics
Standards
2 codes

Quick check

If the learner wants to find out which soil is best for growing beans, can they set up a fair test where only the soil changes and everything else stays the same?

Ask this to see whether the topic is secure.

Topic // Mastery

What mastery looks like

What a learner can do once this topic is secure.
  • Explain what makes a test 'fair' (only one variable changes, everything else stays the same)
  • Identify the variable to change, the variable to measure, and the variables to keep the same
  • Set up and carry out a comparative or fair test with support

Topic // Map

Where this fits

What to learn first and what this topic opens up, with the reason for each link. Required links come first.
  • RequiredMust come first
  • HelpfulHelps, but not essential

Before this

1 topic
  • Simple tests and experimentsRequired

    Scientific Inquiry // Ages 5 to 7

    Must do simple tests before setting up formal fair tests with controlled variables

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Fair testing

Ages 7 to 9 // Method

Leads to

2 topics
  • Drawing conclusions from evidenceRequired

    Scientific Inquiry // Ages 7 to 9

    Must conduct fair tests before reporting on findings from enquiries

  • Controlling variablesRequired

    Scientific Inquiry // Ages 9 to 11

    Must set up simple fair tests before independently planning enquiries with variable control

Topic // Research-informed

Teaching notes

From the Marble Skill Taxonomy. These notes have not been validated in classrooms, so treat them as a starting point for your own judgement.

The approach

For ages 7–9, teach fair/comparative testing through the child-language three-variable frame — change one thing, measure one thing, keep everything else the same — anchored in concrete apparatus (ramps and cars, paper planes, plants, dissolving). Build the necessity of controlling variables by letting an unfair test (two things changed at once) become genuinely uninterpretable, so pupils feel why isolation matters rather than only being told. Complement design practice with recognition tasks (spot-the-unfair-test, sort factors into change/measure/keep-same) and justification dialogue, and honestly name when a fair test is the right enquiry type versus observing over time, pattern-seeking, classifying, or research.

Common misconceptions

  • Thinking a 'fair test' means being nice/taking turns (the everyday meaning of 'fair') rather than a controlled comparison where only one variable changes.
  • Changing more than one variable at a time and still believing the result is trustworthy — not seeing that you then can't attribute the effect to any single cause.
  • Believing every scientific question needs a fair test — over-applying it to questions better answered by observing over time, pattern-seeking or research (the AKSIS over-default).
  • Confusing the variable you change with the variable you measure (mixing up the input and the outcome).
  • Forgetting the 'keep the same' variables entirely — controlling only the obvious ones and leaving hidden variables uncontrolled.

Useful representations

  • The change / measure / keep-the-same three-column planner (the age-appropriate precursor to independent / dependent / control)
  • A side-by-side comparative set-up (e.g. two ramps, two cups, two plants) where exactly one condition differs
  • A 'spot the unfair test' contrast pair — one where two things changed, one where only one changed
  • A simple results table with the changed variable in one column and the measured outcome in the next
  • A predict → test → compare loop card

Teaching practices

  • Teach the three-variable frame in child language on a concrete example first — 'change one thing (the ramp surface), measure one thing (how far the car rolls), keep everything else the same (same car, same height, same push)' — before ever using the words independent/dependent/control.
  • Make UNFAIRNESS the teaching engine: show a rigged test where two things were changed at once (rougher surface AND steeper ramp) so pupils feel that you genuinely cannot tell which change caused the result — this builds the necessity of controlling variables far better than being told the rule.
  • Name the enquiry type honestly and don't over-default to fair testing — the AKSIS research shows fair tests dominate over half of primary practicals at the expense of pattern-seeking, observing over time, classifying and research; help pupils recognise WHEN a fair test is the right tool versus another enquiry type.
  • Use predict-then-test: pupils commit to a prediction before running the comparative test, so the result is something to check against an idea, not just an activity.
  • Keep the number of variables tiny and the apparatus familiar (ramps, plants, materials, dissolving) so cognitive load is on the fair-test reasoning, not on unfamiliar equipment.

Activities to try

  1. 1

    Design the ramp race: isolate one variable

    Why it works: A test is fair because only one thing changed, so a difference in the result that shows up again when you repeat the runs can be put down to that single change; when two things change at once the result cannot tell you which cause produced it.

    1. Set up two ramps and a toy car. For each ramp choose values for the conditions: surface (smooth/rough), height, and starting push.
    2. Choose what to measure — e.g. how far the car rolls.
    3. First deliberately make ramp B BOTH rougher AND steeper than ramp A, run both, and try to say which change caused the difference in distance.
    4. Notice you cannot attribute the result to one cause; then rebuild so only ONE condition (e.g. the surface) differs and everything else is identical, and run it again.
    5. Run each set-up more than once and check the result is consistent before concluding.
  2. 2

    Paper-plane fair test: build it and throw it

    Why it works: Setting up and carrying out a real comparative test requires deliberately holding hidden conditions constant; what you DON'T hold the same (different paper, a harder throw for one plane, a different thrower) is what breaks fairness.

    1. Question: do paper aeroplanes fly further with bigger wings? Using paper and a tape measure, set up a fair test to answer it.
    2. Before throwing, state what you will change (wing size), what you will measure (how far each plane flies), and what you will keep the same (same paper, same throwing spot, same thrower, same effort).
    3. Make a prediction, then throw both planes a couple of times, holding the one-variable rule as you go.
    4. Record each throw's distance in a simple two-column results table (changed variable | measured distance).
    5. Compare the results against your prediction and say which variable was changed, which measured, and which kept the same.
  3. 3

    Spot the unfair test and sort the variables

    Why it works: Recognising fairness and correctly assigning variable roles reinforces the frame; not every question needs a fair test — some are better answered by observing over time, pattern-seeking, or research.

    1. Look at a contrast pair of set-ups: one where two things changed and one where only one changed. Decide which is fair and explain why.
    2. For a given test, sort its factors into three columns: what is changed, what is measured, what is kept the same.
    3. Match investigation questions to the right enquiry type — fair test, observing over time, pattern-seeking, classifying/grouping, or researching — and say why a fair test is or isn't the best tool.

Topic // Standards

Curriculum standards

Codes for the curriculum statements this topic maps to. Each publisher owns its standard text.
The national curriculum in England: Key stages 1 and 2 framework document
KS2L.Sci.WS.1KS2L.Sci.WS.2

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