Hold up a toy car and a small weight (for example a bag of coins or a wooden block). Keep the full group materials trays out of sight until the build step so the hook stays a curiosity beat. A small demo set for step 2 (one newspaper sheet, tape, two book stacks with the same pre-marked class gap of about 20–30 cm) can sit ready on the front table, separate from the group trays.

Key question: What job must your bridge or tower do, and how will we know it worked?

Surface prior knowledge without naming an earlier lesson: children already know that folding can make paper stronger, and that makers plan before they build. Capture two or three quick ideas on the board (fold, roll, triangle, tape well).

STEM eyes: ask where children have noticed strong shapes in the real world — strong cardboard boxes, roof frames, Irish bridges and pylons.

Board stays short: the flat-vs-tube question plus the two focus words. Say fuller meanings aloud during the live demo. Use structure only as plain talk for the bridge or tower itself, not as a third key term.

Front-table demo kit (ready before the lesson; group trays stay hidden): one newspaper sheet, masking tape, two book stacks with the same pre-marked class gap of about 20–30 cm that bridge groups will use, toy car and small weight ready for the quick checks.

Worked model (keep live and short; protect time for the full cycle)

Anchor the demo on one flat-vs-tube contrast and one firmer-join beat. Use the longer wonder–predict–test stems only if the physical result is already visible and a spare half-minute remains.

• Bridge beat (main demo): Rest a flat strip across the same 20–30 cm class gap — it sags. Roll the same newspaper into a tube, tape the edge, rest it across — it holds better. Point out that rolling made a stronger shape.
• Firmer join beat: Show a weak join (tiny dab of tape) peel open under a gentle push, then overlap two pieces and tape both sides so the join holds.
• Tower beat (under one minute): Stand one taped tube on end — it leans. Tape three short tubes into a tripod (or brace the base) and show it stands freer and holds the small weight better. Name the tubes and tripod as strong shapes, and the taped overlaps as firm joins.

If you still have a moment, think aloud: I think rolling and firm joins help the bridge or tower do the job. If it still sags, I could add a triangle brace underneath (a strong shape) and tape the overlap on both sides (a firmer join).

Misconception to head off: more tape alone does not always mean stronger. Shape and how pieces meet matter as much as how much tape you use.

What to expect: many first builds will sag or lean. That is useful data, not failure. Praise testing and strengthening.

Before the lesson (must be fully ready before the clock starts)

• Set out one materials tray per group: newspaper sheets, card offcuts, drinking straws, lolly sticks, a roll of masking tape.
• For bridge groups: mark a clear gap of about 20–30 cm between two stacks of books or two desks pushed slightly apart. Keep the gap the same for every bridge group before the lesson begins (match the step 2 demo gap).
• For tower groups: clear a flat desk space and have the same small weight ready for every tower group.
• Print the Investigation Journal page (one per pupil).
• Keep group trays aside until this step; only the step 2 demo kit is on the front table earlier.

One shared success picture (say this to the whole class before trays go out)

Whether you build a bridge or a tower, success looks the same: free-standing (no hands holding it), at least one strong shape (roll, fold, triangle, or tube), and joins firm enough for a gentle load test. Circulate with that three-point checklist so both choices stay one lesson, not two.

During the build

Groups of three or four work well. Let each group pick bridge or tower so there is a little real choice, but keep the success picture class-wide.

Minimum viable build (mid-build target): by the halfway pause, aim for free-standing with one strong shape and joins firm enough to test. Call a pause about halfway: stop adding new features; spend the remaining minutes firming joins and checking the build stands alone ready for the test.

If a group is not free-standing when testing begins: do not start a brand-new design. Help them strip back to a simpler version that can stand alone for one gentle test (for example two rolled tubes side by side for a bridge deck, or three tubes taped in a tripod for a tower). They still join the predict → load → one change → retest cycle with that simpler build.

Prompts while you circulate: Where is your strongest shape? What happens if you press gently here? How could you make that join firmer without using the whole roll of tape? Is it free-standing yet?

Differentiation: offer a starter idea to a less confident group (two rolled tubes side by side for a bridge deck, or three tubes taped in a tripod for a tower). Stretch a confident group by asking for a wider gap or a second storey on the tower.

Safety: mind fingers when pressing tape and folding card. No running with sticks or straws. Keep the lane clear around bridge gaps.

This step is predict → first load → one strengthen change → retest only. Drawing stays entirely in step 5. Run it as a calm group investigation at each group's own desk, not a race and not a whole-class queue-up. Groups test in parallel while you circulate.

Roles (say this to the class): one child in the group places the toy car (bridge) or small weight (tower); everyone else stands back and watches whether it holds, sags, leans or falls. Swap the placer for the retest if you wish so more children take a turn.

Pacing cue: allow roughly two minutes for spoken predictions, two minutes for the first load and watch, two minutes to make one change, and two minutes for the retest. Keep moving so every group gets both tests; if time is short, shorten the chat after the first test, not the second load.

Bridge test: place the toy car at the middle of the span. Watch for sag, twist or a join peeling open.

Tower test: place the small weight on top (or hang a light bag from a safe point if the design allows). Watch for lean or collapse.

Prediction beat: every group says aloud what they think will happen and why before the first load goes on. Predictions are the start of the science, never marked right or wrong. Link the word load only after naming the familiar object: the load is your toy car or small weight.

Strengthen once: after the first test, groups may change one thing only (add a brace, retape a join, roll a weaker leg into a tube) and test again. Keep the same toy car or weight and the same gap so the comparison is clear.

If a structure fails completely: treat it as useful evidence. Ask where did it give way first — the shape or the join? In the same two-minute strengthen window, simplify one join or one shape for the retest (for example retape the weakest join, or roll one floppy leg into a tube). Do not start a brand-new design from scratch; the group still completes predict → load → one change → retest with the simpler fix.

Safety: everyone except the one placer stands back during the load test. Do not stand on chairs to load a tall tower. Catch falling pieces; mind fingers and toes.

Pupils record on the paper Investigation Journal page. Do not describe invented boxes or columns on the journal — say what to record, not where it sits on the page. This recording happens in class during this lesson sitting; it is not homework.

What pupils should show: a clear drawing of their bridge or tower; strong shapes marked (for example rolled tubes or triangle braces); joins that held; one short spoken sentence to a partner — This made it stronger because…

If time is tight, a labelled drawing plus one spoken sentence to you is enough. No typed reflection.

Look-fors: the drawing matches the real build; the child can point to a shape or join and say what it did in the test.