Display the thermometer reading −3 °C as pupils settle. Take two or three hands-up answers, not open call-outs. Listen for the word below — that is the idea the whole lesson hangs on. Don't correct or explain yet; the minus-sign meaning is built in the next step.

Walk each snapshot aloud, one at a time. Between snapshots, drop in a quick turn-and-name ("tell the person you can see where the next marker will land") to keep the watch beat live.

• −7 — say 'seven steps to the left of zero' and sweep your finger left along the line so the direction lands physically.
• 0 — pause here. This is the make-or-break idea: zero is the middle, not the start. Use the lift-floor image if the class needs a second anchor — ground floor 0, basement −1 and −2 below, floors 1–6 above.
• +5 — draw out that +5 is five steps right and −7 is seven steps left: same idea of stepping out from zero, opposite directions, different distances. Do not let the class think they are equally far out.
• The Galway change — this is where the lesson's key method is built on screen. Take a few first guesses (hands up), then count it out on the marked line in front of everyone: 'four steps down to zero, then two more below zero, four and two makes six.' Sweep your finger through zero so the class sees the count carry on past it. This is the method pupils will rehearse in Try It Together and use in the Class Challenge.

This round rehearses the change-counting method built in Watch and Notice, before pupils meet it in the Class Challenge.

Call the first change (+3 to −1). A pupil comes up and places a marker on +3 and another on −1, then the class counts the steps together: 'three down to zero, then one more below, that's four.' The rest predict the count with a pointed finger showing how many steps before it is placed. Repeat for the bigger change (+2 to −5): 'two down to zero, then five more below, that's seven.' Keep drawing attention to the count carrying on through zero — pupils who stop at zero are the ones to catch. Keep it brisk; this is guided counting practice, not a discussion.

These are the practice questions — pupils take turns at the board, check each answer, and the class confirms before moving on. Every problem asks for the size of the change (a count of degrees), the same task built in Watch and Notice and rehearsed in Try It Together. Keep the board work brisk rather than over-explaining.

• The first problem stays below zero the whole way — a straightforward count. The basement and the Mullingar problems are the pivot: they cross zero, so count down to 0 first, then keep counting below. Watch for pupils who stop at zero.
• The final problem is a big fall from +2 down to −7 — the longest cross-zero count in the set. Revoice: 'two steps down to zero, then seven more below, that's nine.'
• Have pupils name the action word (fell, dropped, colder) before choosing subtract — the size of a change is always a subtraction, even though it feels like counting.