Show a photo of the school building, or point out a window if the building is visible from the room. Take three hands-up guesses in metres, no open call-outs.

Do not reveal any method yet, and do not hint at shadows. Let the question sit as a genuine puzzle: how do you measure something you can never reach?

Walk Method 1 slowly on the board, sketching the two triangles side by side: stick with its short shadow, building with its long shadow. Give Method 1 clear primacy — it is the lesson's anchor.

• Method 1 is the lesson's anchor — emphasise that the two triangles are the same shape because the sun is in the same place, so the shadows grow in step with the heights.
• Pause after Method 1 and ask the class to check the × 10 on the board numbers before you move on.
• The cross-checks (bricks, storeys, comparison) are deliberately brief and visually subordinate — do not give them equal weight to Method 1.

The key teaching point is the closing line: several good estimates that land close together is what builds trust. Say it out loud and underline it.

Lead the whole class outside at the start of this step — budget the first minute or two for the out-and-back walk and getting everyone settled at the flat sunlit spot.

Outside: stand a known-height stick (use a metre stick, height 1 m) vertically. Chalk-mark the tip of its shadow and the base, then measure that shadow with a tape. Immediately chalk-mark and measure the school's shadow from the wall base to the shadow tip — both measurements must happen at the same moment, so have two pupils marking at once if you can.

On a clipboard or back at the board, work it aloud: stick height ÷ stick shadow = building height ÷ building shadow. So building height = (1 m ÷ stick shadow) × building shadow. Have pupils call out each number before you divide.

If it is cloudy and there are no shadows, switch to the brick-count or storey-count method as the shared worked example instead.

Send groups of four or five to fixed unreachable features (a flagpole, a tall wall face, a basketball hoop, a tree). Each group settles at one main feature and investigates it with two different methods, then makes quick single-method estimates of two others nearby.

Each group records into the copybook table set up earlier. Circulate and prompt: which method suits a flagpole? which suits a brick wall? Push for a different strategy on the second method so the two estimates are a genuine cross-check, not the same sum twice.

Close by asking pupils to write one line in their maths journal: the most surprising height they estimated today and how they found it.