Confirm the two rectangles are on screen (or quickly sketch them on the board) before you read the opening line, so you have something to point at. Take three hands-up guesses, not open call-outs, and do not confirm which is right. Some pupils will say "yes, of course" and some "no" — that split is exactly the tension the lesson resolves. Write the two guesses on the board so we can return to them at the wrap.

This is a genuine prediction, not a teaser: the answer is discovered by pupils in Watch and Notice, not revealed by you now.

Don't name the rule up front. Build the three results first, then ask what they notice.

Keep a table going: perimeter 12 each time, areas 5, 8, 9.

1 x 5: fence 1+5+1+5=12, count inside, only 5 squares. Long and thin, least space.

2 x 4: same fence 2+4+2+4=12, two rows of four, 8 squares. Thumbs before the reveal.

3 x 3 square: 3+3+3+3=12, three rows of three, 9 squares, most of all. Pause here so the pattern lands.

Ask: what's happening to the space inside as we go? Revoice a pupil into the rule, closer to a square holds more space though the fence never changed.

Watch for perimeter/area mix-up: point to the edge for one, the inside squares for the other.

Keep saying same fence so the fixed perimeter stays front of mind. Thumbs are their part, no answering aloud.

This round is for talking it through together — individual pupils take turns at the board and the class agrees or corrects out loud. The watching class shows a thumbs prediction before each build; that is their participation.

Individual pupils come up to drag a rectangle to each named size; the class predicts the area before you read it off. Keep saying the fence is always 16 cm so the fixed perimeter stays anchored. Build strictly in the order 1×7 → 2×6 → 3×5 → 4×4 so the areas climb 7 → 12 → 15 → 16 and the square is the key one. Do not name the areas until each is read off the tool.

• If a pupil predicts the 1×7 wrongly high, that's useful — it shows the intuition that "long fence means lots of space" is exactly what today overturns.
• Ask each time: "is this closer to a square than the last one? What is happening to the area?"

These are the practice questions — pupils take turns at the board, check each answer, and the class confirms before moving on. Keep the board work brisk rather than over-explaining. Reveal the three list-items one at a time so only the current job is on screen.

For perimeter 12 cm the full set is 1×5 (area 5), 2×4 (area 8), 3×3 (area 9). A pupil builds each on the tool; the class reads the area and you record it in the board table.

• The point is the closing question: pupils should see the square (or nearest-to-square) rectangle wins. Revoice this into the day's rule.
• Fast finishers wait quietly and predict the next rectangle in their heads — there are no devices at desks for this IWB round; the perimeter-20 hunt is the activity-book page that follows.
• Watch for pupils listing 5×1 as different from 1×5 — agree as a class that these are the same rectangle turned round.