Take two or three hands-up answers, not open call-outs. Listen for on the corner / on the point — that is the vertex, and it is the first thing to get right. Don't confirm the reading yet; the how-to comes next.

• 35° — point at the centre on the vertex and the arm on 0 before you read; acute.
• 145° — the two-scale trap. Ask which ring starts at 0 on the arm, then follow that ring round. The other ring reads 35° and that is the wrong answer to head off.
• 90° — both scales agree here; a good breather.
• 178° — hold out for the difference between this and a full straight line; the reading is easy to miss by a degree or two.

Say the move a pupil should make, not the number: find the 0 on your arm first, then read round.

Talk this one through together. A different pupil comes to the board for each of the three angles; the rest of the class names the ring first and then agrees or corrects out loud once the arm is dragged.

Both scales are on. Before each drag, ask the class to point to the 0 on the arm and name the ring they will follow. 115° and 160° are the ones where reading the wrong ring gives 65° and 20° — head that off by making them name the ring first. Revoice a strong answer: the arm is on the left 0, so we follow the inner ring round.

This is the practice round — real protractors on real angles, so pupils measure at their own desks and the class confirms each reading aloud at the end. Keep the board work brisk rather than over-explaining.

Circulate and catch alignment slips on the spot: the two most common are the centre off the vertex, and reading the ring that does not start at 0 on the arm. Once the round is done, read the trickiest angle aloud together and reconcile any disagreement.