Take three hands-up answers, matching each object to a tool. Keep it brisk — the point is to surface that different measures need different instruments before the investigation starts.

Model the two-step rhythm the class will use: say your estimate out loud, then read the instrument. On the desk-length reading, point out lining the zero up with one end. On the small-object reading, point out where the marker lands on the ruler.

Say the estimate before every reading — that habit is the whole lesson.

This is a small-group station rotation, not a board beat. Groups of four move around the three stations in turn.

Circulate between groups and catch alignment slips on the spot: not lining the zero up on the ruler, and reading a jug from above instead of at eye level. Listen for each pupil saying their estimate aloud before they measure.

If a station's real kit is not available, pass the objects and instruments between groups, keeping the same estimate-then-measure rhythm.

Drive this interactive on the IWB. Point to how each little line is 1 mm, and read the length as 14 cm and 5 mm together. This is the format pupils will write in the round that follows, so make the cm-and-mm way of writing it clear now.