Hold one flat paper strip out from one end so the class can see it flop. Keep the hook light: one surprising flop and the question. Do not name the three shapes yet and do not hand out materials. Pupils watch only; they do not hold strips yet.

Key question: Why does this paper flop when nothing has changed about the paper itself?

Take two or three quick guesses. Do not correct them. Save any talk of paper holding firm until after the first shaped demo later. The investigation will settle the idea.

Keep the board short. Name stiffness and the three shapes in plain language tied to the coming test. On the IWB lead with V, tube and fan folds (ridges). Use concertina only as a light synonym later, once pupils have made the ridges with their hands. Full definitions stay here as your reference, not a script to read aloud. Do not model the full ranked comparison yet: that would give away Step 3's prediction. A short method demo (how to fold and hold fairly) comes after predictions, at the start of the hands-on step.

Misconception to head off: children may say thicker paper is what makes it stiff. Keep every strip the same paper so the only change is shape.

Nature of STEM: steel roofing is ridged (corrugated) so thin sheets stay stiff in Irish wind and rain; scaffolding poles are hollow tubes so they are strong and light. People worked out these shapes long before modern materials.

Use think-pair-share. Predictions are never wrong; they are the start of the science. Do not demo or rank the shaped strips yet. Keep pupil talk on V, tube and fan folds or ridges; if a child already knows the word concertina, accept it, but do not require it yet.

Look-fors:

• Pupils name one shape and give a reason (even a simple one counts)
• Someone predicts the tube; someone else may pick the fan folds

Capture two or three predictions on the board in the children's own words. You will return to them after the hand tests.

Before the lesson

Cut A4 sheets into strips about 4 cm wide and 21 cm long. Each pair needs enough strips for one flat baseline plus one deep V, one tube and one set of fan folds (about four to six strips per pair, with spares). Pre-fold one deep V, one tube and one fan-fold strip per table as support models, especially for the tube and ridges which take longest.

Method-only model (about 3 minutes, before pupils start)

Show how to fold each shape and how to hold fairly. Use the flat strip as the baseline flop only. Do not rank the three shaped strips or announce a winner: pupils must feel that for themselves.

I wonder whether shape alone can stop this paper flopping. I predict (point back to the board predictions). I test fairly like this.

Hold the flat strip out from one end: it flops.

Deep V: fold the strip long-ways so it looks like a tiny roof. Hold it out as a little roof beam sitting upright (point of the V down or up), not flopped on its side.

Tube: roll the strip tightly along its long edge and pinch or lightly tape the join. Hold it out from one end.

Fan folds: fold back and forth into even ridges, like a paper fan, so the ridges run from the end you hold out to the free end. Leave the ridges standing up a little (do not squash the fan flat again) so the strip has depth when you hold it out.

Same length sticking out each time. Nothing under the strip and nothing resting on top.

Tell the class: your folds may feel different from your neighbour's, and that is useful to talk about.

How to run the pupil tests (about 15 minutes)

Scope lever so every pair finishes the compare: pupils work in pairs and share the making. Between them they produce one deep V, one tube and one fan-fold strip (plus one shared flat baseline). Both children must still hold and feel every shape. Sharing the making is what keeps the four-way hand compare inside the slot; do not ask each child to make all three shapes alone. If a pair is slow on the tube or fan folds, hand them a pre-folded support model so they still complete the feel-and-compare.

Time-box roughly: method model (3 min), flat baseline (1 min), make and feel V (3 min), tube (4 min), fan folds (3 min), pair compare (1 min). Circulate and keep the comparison fair:

• Same paper every time
• Hold from one end only, same length sticking out
• No books, no rulers under the strip, no weights on top
• V held as an upright roof beam (point down or up), never on its side
• Fan-fold ridges run from hand to free end and stay standing up a little

How to make each shape (quick reminder after the live model):

• Deep V: fold the strip long-ways so it looks like a tiny roof; hold it as an upright roof beam
• Tube: roll the strip tightly along its long edge and pinch or lightly tape the join so it stays rolled
• Fan folds: fold back and forth into even ridges, like a paper fan, ridges running from hand to free end; leave the ridges standing up a little (do not squash the fan flat again) so the strip has depth when you hold it out

What to expect: the flat strip usually flops at once. A deep V often holds better when held upright. Fan folds often resist well across the ridges when left standing. A tight tube often feels stiffest. Treat mismatches (loose tube, shallow V, squashed-flat fan, V held on its side, ridges the wrong way) as fair-test talk, not errors: ask what changed about the fold or the hold. If a tube unrolls, pinch the join or add a tiny piece of tape.

Key questions while circulating: Is the paper different, or only the shape? Which one would you trust to hold a light card?

Differentiation: hand the pre-folded support models to pairs who need them so the compare still happens. Confident pairs can try a shallower V versus a deeper V (both held as upright roof beams) and say which feels stiffer.

After hands have felt the ridges, you may lightly name them a concertina if useful, but keep recording and talk in fan folds or ridges.

Pupils record on their Investigation Journal page. Do not invent extra columns or boxes: say what to record, not how the page is laid out. Accept fan folds or ridges as the shape name; concertina is optional if a pupil chooses it.

What to record:

• Flat strip: flopped or held
• Deep V: flopped or held
• Tube: flopped or held
• Fan folds (ridges): flopped or held
• Which shape resisted best, in their own words

Observation prompts while they write: Did any shape surprise you? Was the paper the same every time?

If a pupil only drew, ask them to say one sentence about the best shape so the oral conclusion is secure.