Trace your finger right around the edge of the picture frame (or the IWB frame) and back to the start as you read the question. Take three hands-up answers, not open call-outs. Listen for the idea of measuring the edges and adding them — that is the whole lesson in one sentence.

Point to each side as its length comes up. Triangle: three sides, 3 + 4 + 5 = 12 cm, touch each once.

L-shape is the trap: it bends, so six sides, not four. Run a finger right around so nobody skips the two short inside steps. 5 + 2 + 3 + 3 + 2 + 5 = 20 cm.

Square: all four sides equal, 6 + 6 + 6 + 6 = 24 cm. Ask whether we really need to measure all four, to plant the equal-sides idea for next lesson.

Rectangle: two long, two short, 8 + 3 + 8 + 3 = 22 cm.

Throughout, stress touching each side once and only once.

This round is for talking it through together — pupils take turns at the board and the class agrees or corrects out loud.

Call individual pupils up one at a time to click each side of a shape. The rest of the class watches the running total and confirms the final answer. Mix in a four-sided shape and at least one shape with five or six sides so the count every side point keeps getting practised. If a pupil double-clicks a side or skips one, pause and ask the class did the ant walk that edge already?

Two questions to put to the pupil at the board: Which side did you start on, and did you end back there? How many sides did this shape have altogether?

These are the practice questions — set the objects out at four or five stations, with two or three copies of each object per station so a small group can each measure and pass on. Keep the pass-on rhythm brisk; the class confirms each reading aloud at the end. If you have fewer copies, run it as a pass-on chain rather than stations so no object sits idle.

Circulate and catch alignment slips on the spot — the ruler's zero must line up with the start of each edge. The triangle is the key check: its three sides must all be added, not just the two that look obvious. For the desktop stretch, remind pupils a desk is measured in centimetres but may run past 30 cm, so they lay the ruler end-over-end. Reconcile any disagreement on a measurement as you circulate.

Recap the key phrase one last time: add every side, touch each side once. The next lesson builds the equal-sides shortcut, so flag the square and rectangle from today as the bridge.