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Get cross in maths

"Let's play the cross-out game," always produces a cheer. Used as an assessment activity in mental maths, it tells what individuals understand of the number system, and can be used progressively over the years as ability increases. Pupils need individual whiteboards or shared boards to learn the game.

Ask pupils to choose five different two-digit numbers, writing one in each corner and one in the centre of a board. Pupils are then asked to cross out all numbers according to a particular criterion (examples: cross out all even numbers; numbers with both digits the same; any number in sevens column). Extend this weekly as children become more proficient. Once confident, pupils themselves will suggest criteria if given a chance.

Play the game next to a 100 board so you can visually reinforce concepts during the game, for instance, show with a finger what is meant by, "Cross out any number more than 60 in the 3s column."

More able pupils can then help less able ones check the boards. When only four or five players remain, pronounce them the winners. Children play at their own level, the less able or experienced initially selecting numbers under 20. Competitive spirit will ensure they soon begin to select higher numbers. The more able will become highly selective in their initial five numbers, choosing both odd and even, high and low ones. The question "What could I say next to get everyone out?" will reveal those with a growing knowledge of number.

My class of mixed Years 1 and 2 love this game. The more able play it with an adult, selecting three digit numbers as well as two. It is a great activity for the warm-up or end of a mental session or as the plenary, focusing on a particular objective from the lesson. It works brilliantly at key stage 1, but could easily be adapted for a fast game at KS2, extending to four digit and negative numbers, decimals and fractions.

Gwynneth Bailey, language co-ordinator, Aldborough Primary, Norwich

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