• Quick retrieval from earlier learning (Choosing a measuring tool). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Which tool would you use to measure the width of a leaf? (a stopwatch or timer / a measuring jug or cylinder / weighing scales / a ruler or tape measure) → a ruler or tape measurePrompt: Is it a length, a temperature, a mass, a time or an amount of liquid?
2. What could you measure with a stopwatch or timer? (the width of a leaf / how long a toy car takes to roll down a ramp / how heavy an apple is / the mass of a pumpkin) → how long a toy car takes to roll down a rampPrompt: What does this tool measure: length, temperature, mass, time or volume?
3. Zara wants to know if her bean plant grows taller each day. What should she use? (weighing scales / a thermometer / a stopwatch / a ruler) → a rulerPrompt: She wants to know how tall it is.

• Show a simple experiment with one thing changed and ask what makes it a fair test.
• Share the objective: Planning a fair test. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Leo tests which paper towel soaks up the most water. What should he change?
• Step 1: He is testing types of paper towel, so that is the only thing he changes.
• Step 2: So the answer is: the type of paper towel
• Answer: the type of paper towel
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. Mateo wants to know if plants grow better with more light. Which plan is fair? (More water for the plant in the light / Same light for every plant / Same plant type, same water, different amounts of light / Different plants, different water, different light) → Same plant type, same water, different amounts of lightPrompt: Only the thing being tested should change.
2. Which question can be answered with a fair test? (What is your favourite plant? / Is a rainbow beautiful? / Does a heavier parachute fall faster? / Who is the best scientist?) → Does a heavier parachute fall faster?Prompt: A fair test changes one thing and measures another.

• Students work on the student sheet. Circulate and check the first two answers of every student early.
• Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. Fair tests: which statement is true? (If a result surprises you, you should hide it. / You should change as many things as possible. / One try is always enough. / Repeating a test helps you check your results.) → Repeating a test helps you check your results.Prompt: Think about what makes a test fair.
2. Why is it a good idea to repeat a test several times? (To check the results are reliable / To make the test unfair / Because the first try never counts / To change the answer) → To check the results are reliablePrompt: What if one result was a mistake?

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-3.