About 180 pupils aged between 11 and 14 have just spent an hour racking their brains over maths puzzles in a chilly gym at Farlingaye High School in Woodbridge, Suffolk, without a calculator for comfort. They, and 100,000 others from Suffolk to Sutherland, have just done the UK Schools Mathematical Challenge 1993.
None of these mental gymnastics will do them the slightest good in terms of national curriculum attainment targets or Key Stage 3 tests. It is voluntary, at least in the Army sense of the word. It happens because it is someone's idea of fun.
That someone is Tony Gardiner, lecturer at Birmingham University and maths crusader, who runs this burgeoning competition in the teeth of government educational reforms and progressive teaching methods alike.
Operating in typical British fashion, on enthusiasm and a shoestring (entry 30p a head), it has spread in five years to about 1,600 schools throughout Great Britain. 'The aim is that they should come out arguing about the problems and pestering their teachers to talk about them,' Dr Gardiner said.
Do they? As a group of Farlingaye pupils thawed out from the gym they were drawn irresistibly into comparing answers and discussing how to tackle the questions. 'I've just got to know if I've got this right,' said Anya Grieg, 14, as she and Eleanor Garfath- Cox, 13, went into a huddle over the climbing snail question (see question 18).
The pizzas problem (question 16) threw up a variety of approaches. Richard Senior, 12, explained with relish: 'I squashed them all into cubes and worked it out from there.'
The Schools Mathematical Challenge is aimed at 13 and 14- year-old pupils in Year 9, but at many schools, including Farlingaye, the top set in Year 8 also enters.
'They are not like the questions you get in the book. There are different types of maths mixed in one puzzle,' Eleanor said. Anya added: 'Some questions look so daunting. If they just gave you a sum it would be considerably easier, but you get confused by the context.'
Steve Abbott, head of maths at Farlingaye and a former student of Dr Gardiner, feels the challenge does stir up enthusiasm for maths, at least temporarily. It has also shown up some children with an aptitude for maths whose routine classwork was poor.
'You realise that there is more going on in their heads than they are capable of getting down on paper.'
Dr Gardiner is gratified by the spread of the challenge since 1988 and also by the fact that it attracts a complete range, from expensive independent schools to inner-city comprehensives.
'I'm very encouraged by the fact that this has grown at a time when schools are totally swamped and demoralised. Teachers do take on things like this when they see them as useful,' said Dr Gardiner, who is highly critical of progressive teaching methods and the use of calculators. Japanese schools do not permit them until the age of 13, he added.
The aim of the challenge, sponsored by National Westminster bank, is encouragement, not picking a mathematical elite. Of those taking part, 40 per cent will receive certificates - 6 per cent gold, 14 per cent silver, 20 per cent bronze.
However, the best 1,000 students are invited to try the Junior Mathematics Olympiad, a three- hour written paper which, as Dr Gardiner remarked drily, gives them 'a glimpse of what there is still to learn'.