Give five seconds of quiet think-time before any hands go up. Take two or three hands-up answers, not open call-outs.

If you have a real paper butterfly or a folded heart to hand, hold it up and fold it slowly so the class sees the wings meet. Otherwise the photo carries the idea.

Square: board shows the up-and-down fold, both halves land exactly on top. Hold up a paper square, fold it side to side and corner to corner, ask each time whether both halves land exactly on top. They do, so a square has four lines of symmetry.

Triangle with three equal sides: hold up a paper triangle, fold from each corner to the middle of the opposite side, all three match. Your demonstration that a shape can have more than one line of symmetry before pupils try it.

Letter A: board shows the one true fold down the middle, halves match. Deliberately try a slanted fold, ask whether the halves match. They miss. Key point: a fold is only a line of symmetry when the halves cover each other.

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

Call one pupil up at a time to drag the mirror line on the tool. Before checking, ask the rest of the class: do you think the halves will match on that line? Then reveal and let the class confirm or correct.

• Letter T — one line straight down the middle, which the up-and-down tool can show.
• Heart — one line down the middle, again straight up and down.

Then take a paper rectangle and a paper triangle with three equal sides. Fold the rectangle side to side (a true line) and corner to corner (the halves do NOT match — a useful contrast). Fold the triangle from each corner to show its three lines. These folds are not straight up and down, so we do them on paper rather than on the up-and-down tool.

Keep revoicing the test: a real line of symmetry, or mirror line, makes the halves cover each other.

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.

• Heart — 1 line, straight down the middle.
• Rectangle — 2 lines (the up-and-down line shows on the tool; remind the class the slanted folds do not match, so it is two, not four).

After the tool work, finish with a quick spoken discussion: hold up or sketch a circle and ask how many folds would match. The class agrees a circle has far too many to count — any fold through the centre works. Callout to use: is the slanted fold a real line of symmetry, or do the halves miss each other?

Keep this brief. Recap the matching-halves test once more before moving on, and remind the class that the line of symmetry is the same thing we will call the mirror line next lesson.