Fold a real or projected paper heart down the middle so the class sees the two halves land together. Then hold up a square. Take two or three hands-up answers on where a square could fold; do not confirm or correct yet, just collect predictions to test in the next step.

Walk each example aloud, one at a time, dragging the mirror line on screen. Before you reveal each shape's answer, ask the class a quick hands-up question (how many folds do you think will match here?) and take two answers, so the watching class stays with all four shapes rather than only the rectangle.

• Square — emphasise that the corner-to-corner (diagonal) folds also work here; a rectangle's do not.
• Rectangle — pause on the diagonal fold and ask the class to predict before you reveal that the halves miss each other.
• Letter X — the vertical fold matches and the horizontal fold matches; two lines.
• Letter T — only one vertical fold matches.

This is display mode — narrate and point; nothing is dragged by pupils yet.

This round is for talking it through together — pupils take turns at the board and the class agrees or corrects out loud.

Name a shape, then send one pupil up to drag the mirror line and test it. Ask the class did the halves match? before confirming. Watch for the common slip on the rectangle: pupils try a diagonal fold expecting it to work like the square's. Revoice: so the diagonal works on a square but misses on a rectangle. Rotate four pupils across the four shapes.

This round is the practice bank — 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.

The letter S is the trap: it looks balanced but no fold makes its halves match, so the answer is zero lines of symmetry. Let pupils try a fold and discover the miss rather than telling them. Revoice the big idea: looking balanced is not the same as having a line of symmetry. Press the Check button after each pupil sets their lines.