Key Stage 3 design and technology · Evaluate

KS3 design and technology: testing and refining a product

In Key Stage 3, design and technology pupils are taught to test, evaluate and refine their ideas and products against a specification, taking into account the views of the people who will use them and other interested groups. A project is not finished when the product is made. It is finished when the pupil can show, with evidence, how well it meets what it was meant to do, and what they changed to make it better.

Testing and refining a product, explained

Everything in this topic starts with the specification, the list of requirements the pupil wrote at the beginning. A good specification has points that can be checked, such as “holds at least 750 millilitres” or “can be opened with one hand”. Testing then simply means checking each point and recording the result. If the specification was vague, the testing will be vague too, which is why teachers insist on measurable points early on. The curriculum links the two: pupils develop specifications to inform design, and then test the finished product against them.

Pupils carry out different kinds of test. Some are measurements: the volume a container holds, how much weight a shelf supports, how long a battery lasts, how many seconds a mechanism takes. Others are performance tests, such as dropping a prototype from a set height or opening a catch twenty times. Others rely on opinion, where users try the product and answer questions. A fair test changes one thing at a time and repeats it, because a single result can be luck. Results are recorded in a table, often with a pass or fail against each specification point.

The views of intended users matter at least as much as the measurements. The curriculum names “intended users and other interested groups”, which means people who are not the main user but are affected by the product. For a school lunch box, the user is the pupil, but parents who pay for it, teachers who see it in the classroom and the people who wash it all have views. Pupils learn to gather feedback carefully: asking open questions rather than leading ones, such as “what was difficult about opening it?” instead of “was it easy to open?”, and asking enough people to see a pattern.

Evaluation is the thinking that follows. Pupils decide which results matter, explain why something failed and suggest what would fix it. The skill teachers look for is moving from “it did not work” to “the lid is too stiff because the catch is 4 mm too tight, so I will make it looser”. They also look for honesty. A pupil who reports that two of five specification points failed and says why shows better understanding than one who claims everything worked.

Refining means making a change and then testing again. This is the iterative process at the heart of design and technology. The best refinements change one thing, address a specific failed point and are checked afterwards. Sometimes a refinement fixes one problem and creates another, so the cycle may repeat. A clear record of what was tested, what was learnt and what changed is what teachers want to see in your child’s folder.

Words your child will hear

Specification: A list of requirements for a product, each written so that it can be tested.
Evaluate: To judge how well something works, using evidence, and to say why.
Refine: To make a careful change to improve a design after testing.
Fair test: A test where only one thing is changed so that any difference in the result can be explained.
User feedback: Opinions and observations gathered from the people who try or use the product.
Stakeholder: Anyone affected by a product, not only the main user, such as a parent or a teacher.
Iteration: One cycle of making, testing and improving. Designs often go through several.

What the National Curriculum says

The programme of study for Key Stage 3 says:

When designing and making, pupils should be taught to test, evaluate and refine their ideas and products against a specification, taking into account the views of intended users and other interested groups
When designing and making, pupils should be taught to develop specifications to inform the design of innovative, functional, appealing products that respond to needs in a variety of situations

Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.

Try it: testing and refining a lunch box prototype

A pupil has made a lunch box prototype. One specification point says it must hold at least 750 ml. How do they test it, gather views and refine it?

Pick the specification points and decide how each will be tested.

1. Holds at least 750 ml: measure
2. Opens with one hand: 5 users try
3. Survives a 1 m drop: drop 3 times
4. Fits a 30 cm wide bag: measure

Test the volume. The inside measures 14.6 cm × 9.8 cm × 4.9 cm. Since 1 cm³ is the same as 1 ml, the volume is the product of the three lengths.
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14.6 × 9.8 = 143.08
143.08 × 4.9 = 701.1 cm³ (to 1 d.p.)
701 ml is less than 750 ml: FAIL
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Gather user views. Five classmates try the box. All five open it with one hand, but three say the lid is hard to close. Because the number is only five, the pupil treats it as a clue, not proof, and asks a parent and a teacher as well. They also notice the box survives all three drops without cracking.
Decide on a refinement that targets the failed points and changes as little as possible. The pupil makes the box longer and loosens the lid catch slightly, leaving the width and height alone. Each change targets a different failed point, so each can be checked separately. The new inside size is 15.7 cm × 9.8 cm × 4.9 cm.
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15.7 × 9.8 = 153.86
153.86 × 4.9 = 753.9 cm³ (to 1 d.p.)
754 ml is at least 750 ml: PASS
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Re-test everything that might be affected. The longer box must still fit the 30 cm bag, and the lid must close more easily without opening in a drop. The pupil records both results and writes one sentence on what to improve next.

The first prototype failed the volume test (about 701 ml against 750 ml). After a targeted change the volume is about 754 ml, which passes. The evaluation is strong because it uses measurements, user views from more than one group, a change aimed at the failed point, and a second round of testing.

Common mistakes and how to help

Treating the test as a way to prove the product is good

Pupils are proud of their work and a failed test can feel like a personal failure, so they choose easy tests or ignore bad results.

What helps: Present testing as a way to find problems early. Say that designers want to find the faults before the customer does, and praise an honest “this failed because…”.

Writing evaluations that only say it was good or bad

Opinions come easily, but linking a result to a specific cause and a fix takes more thought.

What helps: Use a three-part pattern: what the result was, why it happened, and what change would fix it. For example, “it leaked, because the seam is not sealed, so I will add a second row of stitching”.

Changing several things at once

When a pupil wants the product to work, adding many improvements feels efficient.

What helps: Ask which change fixed which problem. If several things changed, the pupil cannot tell. Change one thing, re-test and record the effect.

Only asking friends who will say it is great

Friends are easy to ask and want to be kind, so the feedback does not help.

What helps: Ask the intended user and at least one other group affected. Use open questions and let the person try the product while the pupil observes without explaining.

How to help at home

Write a testable requirement. Pick something in the house, such as a school bag, and write three requirements that can be tested, such as “holds six books” or “can be put on with one hand”. Then test them.
Be an honest user. Let your child watch you try something they have made without explaining how it works. Say aloud what is confusing. Observing quietly is a skill that real designers use.
Try a fair test. Compare two home-made paper aeroplanes, changing only one feature such as the wing fold. Fly each one three times, measure the distance each time and compare the averages.
Keep a change log. When your child makes something, ask them to record each version in a sentence: what was tested, what failed and what they changed. A short log shows the improvement clearly.
Ask different people. Ask a grandparent and a younger child what they think of the same everyday item, such as a jar or a door handle. Compare what each notices to see why different groups matter.

Builds on

Key Stage 2: Analysing existing products
Key Stage 2: Design criteria and evaluating work
Key Stage 2: Inventors and designers who shaped the world