Are your pockets feeling lighter lately? Don’t despair, it may not be impending poverty, just the difference caused by the new, smaller 50p piece, introduced last month. They may be easier to handle, but their introduction will inconvenience some people such as phone companies, slot-machine operators and, of course, primary school teachers. Every time a coin shrinks or is discontinued, or a new one introduced, a host of games, books and other resources must be replaced.

It is more than 25 years since the 50p coin was first circulated, and its shape no longer seems strange. One child I spoke to said she thought the shape was lucky. Another speculated that the coin was made as it was to accommodate the form of the Queen’s nose.

I did wonder what children would make of the picture of Britannia on the back of the coin, hardly a familiar image today. I was put straight on the matter by a six-year-old with a gappy grin brandishing a 50p piece found under his pillow. Apparently, 50p is now the going rate for a tooth and as he turned the coin over and pointed to the picture of Britannia he said: “You can tell it’s from the tooth fairy, it’s got her picture on it.”

These children were familiar with coins. But young children have several difficulties to overcome in a system which may appear illogical. Many small children are dismayed to see 20 1p pieces swapped for a single 20p coin and can’t help feeling they are losing out. The hurt somehow seems greater if the original 1p coins are new and shiny. Nor is it easy to see why a 5p coin is bigger than a 2p, or why we might count three coins and reach a total of 17p.

Many schools use real money when teaching coin recognition, although plastic and cardboard money is used too. Looking through catalogues of maths equipment I have often been amused at the price of dummy coins. I knew 12p coins were on the way out when the cost of paper substitutes exceeded 12p. And I remember the time I spent as maths co-ordinator tippexing the 12ps out of textbooks when the coins were withdrawn. Inflation is hitting the 1p coin now. I have recently seen cardboard 1p coins for sale at Pounds 3.25 for a bag of 250. If you go for plastic coins, which are more durable but even less realistic, you can spend Pounds 2.30 on 100 2p pieces.

A stock of plastic or cardboard money has a place in many infant classrooms, often as part of a class shop or cafe. As a frequent customer of such establishments over the years, I can confirm that the prices are reasonable, the service is friendly and I am only occasionally short-changed. The only real drawback of shopping this way is that you have to return your purchases as soon as you leave the premises.

Money has been an established part of the primary curriculum for many years and its relevance and usefulness require little emphasis. It was perhaps surprising therefore that mentions of money in the original version of the national curriculum were few and vague compared with the detail given to aspects such as algebra or data-handling. Subsequent versions have given it only a slightly higher profile. But it seems more importance is being attached to ability to handle money and carry out the resulting calculations.

Recent concern about mental calculation has raised the profile of calculations related to money. Shopping is an excellent setting for developing mental arithmetic skills. Class shops, money games and work based on catalogues and advertisements can all play a part. Methods used by shoppers and shopkeepers for finding totals and calculating change may differ from the formal written methods often taught in schools. This is a good context for showing that the method selected may be influenced by the number involved. The change from Pounds 5 when spending Pounds 3.99, for example, is easier for many of us to calculate mentally than using a pencil and paper.

Money calculations also find favour in the draft framework for numeracy, recently produced as part of the National Numeracy Project. Such problems are included in the work of every year group from Year 1 to Year 6 and much detail is given.

It is interesting to see how the ideas develop across the six years, with activities for the older children including calculation of VAT and conversion to foreign currency. Here is a good reminder that money calculations do not end when children become too old to sing “Five Currant Buns” or to play in the class shop. Despite the advent of credit cards and electronic tills most of us carry out financial calculations from time to time, if only to find out where it has all gone.

The days have passed when you could brag about getting change from a ten shilling note, but money still makes the world go round. Coins, including the new 50p, are likely to have a central place in the maths curriculum. And the 50p should also lighten the load of the tooth fairy.

Jenny Houssart is a lecturer in mathematics education at Nene College, Northampton