Education is the latest battleground in the war of the supermarket giants. Four chains - Asda, Sainsbury, the Co-op and Tesco - encourage shoppers to collect vouchers that can be redeemed for equipment to shore up resource-starved schools.

A Tesco spokesman calls it “cause-related marketing” and “a virtuous circle creating win-win situations”. Translated into normal English, this means that when sales drives are linked successfully to an unconnected good cause, then everybody gains. Shops attract trade from their rivals and get free publicity (such as this article). Some would argue, as did a spokesman for the School Curriculum Industry Partnership quoted in a Sainsbury press release, that any initiative which brings education and business closer together is a good thing in itself. And it is undeniable that schools can garner a good deal of equipment from this relationship.

For the past five Easters - and probably the next five - a frantic gathering of Tesco’s Computers for Schools vouchers has converted into Pounds 28 million-worth of school computing equipment.

Asda’s Best for Kids ran for the first time last spring, and around 8, 000 schools persuaded parents and children to collect vouchers that could be traded for Compaq computers.

The Co-op runs a voucher-for-musical-instruments scheme, and last year Sainsbury’s devised Schoolbags, which led to 16,000 primary and 2,500 secondary schools organising voucher collections. Schoolbags put an environmental spin on “cause-related marketing” for, in addition to vouchers being issued for every Pounds 10 spent, they also went to customers who brought their own plastic bags. Thus Sainsbury’s marketing director, who is planning a “son of Schoolbags” this year, boasts of the “tremendous environmental benefit of saving 1 million litres of oil in carrier bag production”.

The scheme resulted in many schools dipping into a catalogue for crayons, footballs, guitars, computers . . . everything, in fact, but a new physics teacher.

Many schools are delighted with the voucher schemes. The Lord Grey comprehensive in Bletchley, Buckinghamshire, has refined voucher collecting into a profitable art. Prizes go to the pupil and tutor group that gather the most Tesco vouchers, and the school swaps Sainsbury’s for Tesco vouchers with its feeder school.

David Broadhurst, the IT teacher who has organised Tesco voucher drives at Lord Grey for the past five years, believes it has benefited the school to the tune of Pounds 5,000 worth of new kit. This includes two top-of-the-range Acorn A5000s, a Canon Ion camera, digitising software and control boards, and an Acorn Pentium 100 personal computer.

Broadhurst has a complex view of voucher schemes. He welcomes the way they’ve enabled him to buy specialist equipment that has acted as a pump-priming mechanism for his school’s computing activities. He says that no parent has objected to the mild coercion which has them doing their food shopping at Tesco.

“Schools,” he says, “are affected by the market as much as anybody else. My personal belief is that these days everything is finance-driven. That’s part of school life, and I think Tesco uses this fact to make a profit and look good at the same time. I know that Tesco makes a lot of money from its vouchers while saying to the world, ‘Look at our sense of social responsibility’. Having said that, I wouldn’t knock them and would rather they did it than not. Tesco is helping us to deliver a good experience to pupils.”

There are harsher voices of dissent querying the principles behind education-based sales promotion and questioning who wins the most in the marketeers’ “win-win situations”. Maurice Plaskow, chairman of the Education Forum, a group set up by the National Consumer Council, says: “Education is a common good which should not be dependent on charity, and it is a sad reflection on funding that schools must get equipment in this way. Supermarkets are obviously in business to make a profit and are under no obligation to offer a balanced diet. Schools are different, and they have an extra moral responsibility which commerce does not. If these schemes are an attempt to raise the status of business, I think they are taking an unfair advantage. ”

A recent National Consumer Council report on sponsored curriculum material had this to say on school vouchers: “They effectively reward schools whose parents are pestered to shop in particular supermarkets. At worst, they can marginalise pupils whose families do not have access to these supermarkets or whole schools in poorer areas - or small rural schools - where such stores may not exist at all.”

The benefits to supermarkets, however, are overwhelming. Tesco’s Computers for Schools 96 scheme required parents to spend Pounds 125,000 to Pounds 150, 000 over 10 weeks, to buy one computer with an approximate high-street value of Pounds 1,000 to Pounds 1,500.

That’s 1 per cent, or the tenth part of a tithe - hardly enough to justify any communitarian rhetoric. While the supermarkets are happy to emphasise how you will win, they are coy about their benefits, although their payback is open to guesstimates. Tesco’s Pounds 28 million-worth of computer vouchers translates into around Pounds 2.8 billion-worth of groceries. Tesco’s most recent annual pre-tax profit on Pounds 13 billion-worth of sales was Pounds 681 million, or about 5 per cent; 5 per cent of Pounds 2.8 billion is Pounds 140 million. This, very roughly, is how much Tesco has profited from Computers for Schools.

Asda’s scheme represents better value than Tesco’s, in that expenditure of Pounds 75,000 brings enough vouchers to get a Compaq 486 worth Pounds 1, 200. Its Best for Kids is also good for Asda profit margins, whose marketing department would be aware of the other benefit that completes its “virtuous circle”: the commercial advantage of impressing retailing logos on the children’s minds and of securing new adult customers who believe they are doing something good for schools.

A Consumer Association Which? report in September looked at supermarket “loyalty cards”. It concluded that they represented low-price loyalty because, like school equipment vouchers, they reimburse consumers by only a penny in the pound. Which? advised consumers to go for the discount, while remaining mindful of its value in relation to goods purchased. So, as with any marketing wheeze, it’s buyer beware: never look a gift goose in the beak, and remember that it must be fed expensively before any golden eggs get laid.