Junk food in schools is a hot topic, what with Jamie Oliver and the rise in teenage obesity. And school canteens are at the centre of the battle over children's eating. Parents and schools are both keen to encourage more pupils to use their canteen, rather than the local chippie - and to make sure that they eat healthily when they are there.

Oxfordshire software company Gladstone, which made its name with computer systems for leisure centres, is hoping to cash in on the concern, by offering a product which it claims can be used to boost healthy eating.

St Clare's, in Summertown, is one school which already uses "cashless catering", where students use a smartcard, rather than cash, to pay for food and drink. A fee-paying international school with boarding houses, it had different problems from ordinary state schools, which use cards to avoid the stigma of free school meal children.

St Clare's plumped for the system because it needed a replacement for swipe cards which were always going wrong, leading to long queues when all the students arrived at the snack bar at once at break time.

Bursar Paul Mason said the main reason for introducing the system was to control access to catering services, control costs and allocate the costs fairly.

Business manager Richard Gorst said: "The old cards didn't have a time limit, so students would buy 24 bottles of mineral water and hoard the bottles in their room until they were past their sell-by date. For some reason, they thought that if they didn't use it, they were missing out, but it led to massive food waste.

"This system encourages them to have three meals a day, and to get up in time for breakfast, and parents like that.

"They have a set amount to spend, and if they use it to buy coke and buns at break time, they won't be able to buy lunch. But in fact, because most of our students are from overseas, they eat healthily anyway.

"It does reassure parents that their child is not living on just chips."

The head of IT, John Boschen, said: "If we wanted to, we could easily have web pages showing exactly what each student has eaten, but we don't use that facility. If we were asked - perhaps because of an eating disorder - we could do it."

Instead of electronic cards, some schools use a biometric system, which recognises students' fingerprint. To pay for meals, students present their finger to a scanner at the till, which checks their identity and deducts the bill from their account.

He added: "The main issue for us was whether to go for biometrics or cards, and cards won. But with hindsight, one of the problems we have with our attendance system is that teachers don't always get it right and don't record correctly who they have in their classes.

"With fingerprinting, that problem would disappear, but there's a stigma attached to fingerprints."

There is also the problem of students losing their cards - some teenagers seem to lose things almost as soon as they are given them. St Clare's says it has almost solved this problem by charging a swingeing £20 to replace a lost card - something which state schools would find it hard to copy.

Peter Doyle, of Wallingford-based Gladstone, is convinced that biometric systems are the way forward, particularly for primary schools - despite parents' fears of 'Big Brother' technology and infringement of personal liberty.

"A few years ago, we had a massive fuss about using credit cards on the Internet. People were worried that their identities and bank details would be stolen, but you only have to look at the figures for Internet shopping to see that we got used to it very quickly.

"We will get used to biometrics in the same way."

Gladstone emphasises that the system being offered to schools does not store an actual image of the student's fingerprint. Instead, measurements are taken that capture the uniqueness of the fingerprint but do not capture the complete image. Data protection laws prevent the technology from allowing the fingerprint to be reconstructed from the data.

"You are taking partial prints, which can't be used anywhere else," said Mr Doyle.

He believes that students will gain from the reduced lunchtime queues and protection against theft of money or cards by bullies, while parents will welcome the chance to top up their child's account online, rather than sending them off with dinner money. They can also tell the school about their child's special dietary requirements.

Schools, meanwhile, can record and monitor what students eat, helping stock control and reducing waste.

Smartcards can be used in lots of other clever ways. At St Clare's, for example, students can only gain access to areas where they are allowed. The girls' dormitory door, for example, will only open to those who are supposed to be there, providing an additional security measure for anxious parents.

However, the outcry over plans to introduce biometrics to identify domestic travellers at Heathrow's Terminal 5 suggests that Mr Doyle may have an uphill struggle to convince us of the benefit of fingerprint recognition systems in primary schools.

As Mr Gorst says, fingerprinting at St Clare's might prove the last straw for some foreign students, who are being given an increasingly hard time by immigration officials.