On the board is a jumble of mixed shapes: flat shape cards, solid objects and angle cards, all mixed up together.

If you had to put all of these into just a few groups, what groups would you choose? What would your rule be?

Your teacher will show two finished sorts using the real cards. Someone has already sorted the cards into groups. Your job is to check whether every card really obeys the rule.

The first sort answers: which of our shapes have right-angle corners? Look at each finished group and decide if every card is in the right place. Then the second sort answers: which of our solids roll? Read each group the same way.

Look carefully at the group a card was put into. Can you find the card that does not belong in its group?

Today we sort these shapes together on the board. We sort by one rule at a time. Before each card moves, say which group it belongs in, and why.

• How many sides? Sort into 3 sides, 4 sides, or more than 4 sides. (triangle, square, rectangle, pentagon)
• Rolls or does not roll? (ball, tin, dice, box)
• Compare each angle to a right angle: smaller, the same, or bigger. (narrow angle, square corner, wide angle)

Today we work through four sorting rounds on the board. Each round is a little harder than the last. A property is one feature of a shape, like how many sides it has, whether it rolls, or the size of an angle. Say your sorting rule out loud before you start each round, then keep to it.

• 2D shapes by number of sides.
• Solids that roll or do not roll.
• Angles — smaller than a right angle, the same, or bigger.
• A mix of shapes sorted by whether they have a right angle.