Display the ruler-and-pencil photo as pupils settle. Take three hands-up answers, not open call-outs. Listen for anyone who reads the tiny marks between 16 and 17 — that is the millimetre reading we are after today. Don't confirm the answer yet; the demonstration ruler will settle it.

This is a real demonstration ruler at the front, not an on-screen widget. Lay each pre-measured object flat against the ruler one at a time.

• 12.4 cm pencil — count the four small marks aloud past the 12 line, then say twelve point four centimetres, or one hundred and twenty-four millimetres.
• 24.7 cm book, 19.5 cm pencil case — show these two as the further objects, same routine, naming both unit versions each time.
• Parallax — lean deliberately to one side so the class sees the line appear to slip, then come back square-on. Say eye square over the mark and have them watch the difference.

Do not solve the Getting Started photo for them — they'll read their own objects next.

This round is for pupils to measure at their desks with their own rulers — circulate and catch alignment slips on the spot. The class reads aloud and you reconcile any disagreement as you circulate.

Look-fors as you walk the room:

• End at zero — many pupils start the object at the left edge of the ruler, not at the 0 mark. This is the most common slip.
• Eye-square lean — gently move a pupil's head straight over the mark when they read at an angle.
• Both unit versions — if a pupil only gives centimetres, ask and in millimetres?

Take a few readings aloud at the end; where two pupils disagree on the same kind of object, re-measure one together at the front.

This round is the practice bank — run the six real objects as rotation stations at the front. Pupils come up in turns and read each object they reach with their own ruler; they record straight into the three-column table they ruled in their maths copy. There is no printed sheet to prepare.

Pupils read as many objects as they can reach in the time rather than a fixed number; keep the rotation moving so as many as possible get a turn, and confirm each reading aloud at the end.

Approximate true lengths for confirming the final readings: crayon ≈ 8.6 cm (86 mm), eraser ≈ 4.7 cm (47 mm), glue stick ≈ 15.2 cm (152 mm), highlighter ≈ 13.8 cm (138 mm), marker ≈ 14.5 cm (145 mm), colour pencil ≈ 17.3 cm (173 mm). Your own objects may differ by a millimetre or two — what matters is that readings agree across the class.

• If you have more than one set of objects, run two or three parallel stations so more pupils read at once.
• The trickier reads are the ones whose ends fall between two millimetre marks — head this off by reminding pupils to take the nearest mark, not a half.

Keep this brisk. The millimetre-reading skill feeds straight into the unit-conversion lesson that follows.