FINGERPRINT data of more than 7,000 children has been obtained by secondary schools in Cornwall.
Figures obtained under the Freedom of Information Act show that more than a third of secondary schools in Cornwall have collected the fingerprints of their students using electronic scanners since the technology first came into use nearly ten years ago.
However, in one of the 12 schools – Falmouth – only 361 students out of more than 1,000 on the roll are using the technology, prompting concerns it is a waste of taxpayers' money. The systems can cost more than of £25,000.
Since September 1, the law says schools must have written parental permission before collecting biometric data from students.
But critics claim the information could still fall into the wrong hands, that it is a breach of children's privacy and an example of a "Big Brother society".
One campaign group also feared schools were not being "transparent" about use of the data.
However, secondary schools said the technology was safe, many using the scanners for cashless catering systems, recording attendance or book borrowing.
John Perry, head teacher at Fowey Community College, where 594 pupils use the technology, said: "We decided to move to biometrics in the autumn term for ease of use. Previously we used plastic lunch cards which were often lost or broken.
"Fingerprint technology enables us to run a more efficient canteen. We're also able to track that students are eating a proper lunch."
In several schools students place their thumb in scanners throughout the site which identifies them and allows access to take out a library book, log attendance or pay for food, with money automatically debited from their account.
The scanner converts the print into a code to identify the individual using a biometric algorithm.
All the schools which confirmed their use of the technology said the data was deleted once the student leaves, and was not stored on mobile devices.
In Helston, where 818 students used biometric technology, a spokesman said the possibilities of fraud were slim, as it is nearly impossible to reproduce a fingerprint.
"We have previously used an electronic card system for attendance and the frequency of lost and forgotten cards was horrendous.
"With biometrics this is clearly not an issue," the spokesman added.
"Pin numbers are provided for those who do not wish to use biometrics."
Treviglas College in Newquay also uses the technology, with 407 of its pupils using the system.
"Biometric functionality came as part of a cashless catering solution," said a school spokesman.
"We wanted to change to a cashless solution to ensure consistency in payment methods for all our students, whether entitled to free schools meals or not."