Competition between supermarkets in Britain to sell ever-cheaper school clothes risks worsening the exploitation of factory workers abroad, charities have warned.
They are urging teachers to talk to pupils about the impact low prices of uniforms can have on workers trapped in poverty in countries such as Bangladesh.
Asda has been at the forefront of the price-cutting, this month offering parents the "lowest ever priced school uniform" for Pounds 4, while Tesco and Marks amp; Spencer are offering them for Pounds 3.50 and Pounds 6.50.
The anti-poverty charities War on Want and Labour Behind the Label said they were concerned at the effects the price war was having on clothes makers. Many found it increasingly difficult to feed their families and educate their children.
Labour Behind the Label visited factories in Bangladesh last year where school uniforms were being produced for Asda, Tesco and Marks amp; Spencer, and found that some workers could barely afford food. Samantha Maher, the charity's policy co-ordinator, said the rising cost of food, inflation and the lower prices at which schoolwear is sold since then would have made workers' difficulties far worse.
"There are factories where they are providing a bowl of rice a day because their workers cannot afford to buy it themselves," she said.
"School uniforms are not high quality clothing and the supermarkets are making massive bulk orders, but there is no way you can produce them for such a low price and pay workers a living wage."
A worker at a Sri Lankan factory producing school skirts for Marks amp; Spencer told the charities last year that her wages were insufficient as her cost of living increased daily. "We work all week, yet we can't afford the basic things we need," she said.
She and her colleagues received 10p out of the skirts' Pounds 6 selling price. This year, the store has been selling school skirts for Pounds 3.50, although it said the price cut had not been passed on to its suppliers.
Asda, Tesco, and Marks amp; Spencer have all emphasised their commitment to producing clothes ethically and are members of the Ethical Trading Initiative, an alliance of companies and charities which aims to improve working conditions around the world. All three arrange independent audits of factories which produce their clothes, and insist their owners pay at least the local minimum wage.
Ms Maher said that such schemes had helped stop child labour and protect workers from certain health and safety risks. But workers making school uniforms and other clothes still received poor wages, could be prevented from forming trade unions and could face discrimination and harassment from their employers.
These concerns were shared by Simon McCrae, senior campaigns officer at War on Want. "How many kids in Bangladesh can't go to school themselves because of a price war in Britain over uniforms?" he said. "You are benefiting as someone is being exploited". He stressed it was important to teach pupils about how their clothes were made so they could try to make a difference, rather than feel ashamed of their parents' choices.
Asda has sold more than 11 million items of its George brand schoolwear in Britain in the last 12 months, selling 1.6 items a second during its busiest week.
A spokeswoman for Asda, a division of US giant Wal-Mart, said that it was not paying its factories any less and that it was able to drop the price by reducing its profit margins, selling the clothes as a "loss leader" to attract customers.
She said that it was difficult to agree what a living wage should be. "Asda, as a retailer, is at least two steps removed from the workers we want to support, which means that wages aren't controlled by us," she said.
But she added that pressure by the international Multi-Fibre Agreement Forum, of which Asda was a member, had helped lift the minimum wage for garment workers in Bangladesh from 940 takas (Pounds 7) to 1,600 takas (Pounds 12) a month in 2006. Labour Behind the Label believes workers there now need a monthly living wage closer to 5,000 takas, about Pounds 38.
Marks amp; Spencer
For children aged 3 to 6:
Polo shirt Pounds 1, based on three polo shirts for Pounds 3
Skirttrousers Pounds 3.50
Jumpercardigan Pounds 2
Total Pounds 6.50
Produced in Bangladesh, Sri Lanka and China
"We audit all the factories we source from, including those making our Back to Schoolwear ranges. The audits check that our standards are being met, which include: no child labour, and that working hours should not be excessive."
For children aged 3 to 12:
Polo shirt 50p
Skirttrousers Pounds 1.75
Sweatshirt Pounds 1.75
Total Pounds 4
Produced in Bangladesh, India and Turkey
"We are really open about our ethical practices. Our low prices are because we buy material in quantity. They are also because of the margins we make, which in the case of uniforms are negative: we make a loss."
For children aged 3 to 5:
Polo shirt 75p
Skirttrousers Pounds 1.75
Jumpercardigan Pounds 1.75
Total Pounds 3.50* based on three-for-the-price-of-two discount, saving 75p
Produced in countries including Bangladesh
"We are committed to improving the lives of workers. The alternative would be for us to stop sourcing in countries that have problems which are beyond the capabilities of any organisation working alone to fix. But we don't think that is right for the people or what our customers would expect us to do."