Some schools have brought in fingerprint and eye scanners, while others are planning to put radio transponder chips in pupils' uniforms to keep tabs on them.

One school installed an iris scanner in 2003 but removed it a year later after it failed to recognise some students and led to lengthy queues.

Aurora, a Northampton-based biometric firm, will exhibit its new "face recognition software" at an education technology conference in London next week.

The company has developed a prototype aimed at schools for "ultra fast student registration, easy cashless catering and secure access control".

Each system - costing around £1,000 - can verify a face in 1.5 seconds and claims to be more accurate at identifying people than a human.

Patrick Usher, the company's technical director, told the Times Educational Supplement that adapting the technology for children was a challenge as their faces changed quicker than adults.

John Dunford, general secretary of the Association of School and College Leaders, said the system would be welcomed if it cut bureaucracy - but he said: "You always seem to get queues behind security devices".

But civil liberties campaigners are concerned that the data could be given to police or the Government without parents' knowledge - or stolen by identity thieves.