Take three hands-up answers, not open call-outs. Hold out for the trickier third question: how did you read the marks with no number? Do not resolve it yet — that is the whole lesson.

Ruler on screen: pencil's right edge falls between 14 cm and 15 cm, halfway across the mm divisions, so 14.5 cm.

Point to two numbered marks, have the class count the small gaps before reading the pointer — this is the load-bearing move. Say the rule: work out one division first, then read.

Hold up a real ruler: read it from directly in front, then deliberately from the side so the reading shifts. Name it — parallax.

Real jug: marks 0 and 500 with 5 equal gaps, so 500 ÷ 5 = 100 ml per mark; water at third mark reads 300 ml.

Real mass scale: each small mark 50 g, needle two marks past 1 kg reads 1.1 kg.

Scale and jug are done with the real instruments, not on screen — the ruler is the only on-board example.

The length reading is individual (every pupil has a ruler); the mass and capacity are taken in turn on the shared group scales and jug. To stop a queue forming, stagger the start: have some groups begin with the mass reading and others with the capacity reading, so both shared instruments are in use at once. Circulate and catch alignment slips on the spot.

Listen for the value-of-one-division step being skipped — that is where readings go wrong. Revoice a good example: five gaps to 500 ml, so each mark is 100 ml.

This is the practice round — groups measure the long edge of each surface with their own instruments and rank the three lengths. Keep the rhythm brisk; the class confirms each length ranking aloud at the end.

Manage the out-of-seat measuring safely: pick a notice board or wall display at a comfortable standing height rather than a window, and have only two pupils per group up and measuring at once while the rest record. Watch for the value-of-one-division step being skipped and for readings taken from the side. Prompt with read it square-on — what is one small mark worth? Ranking by length gives weaker readers a foothold: they can order by length even if a single reading is imperfect. The stretch prompt about error feeds directly into the journal beat.