A row has broken out over a Cambridge school's plans to fingerprint pupils.
Head teacher Tony Davies said few parents were now upset
St Matthews School brought in the new security system as an alternative to library cards but the proposal has sparked a row with parents.
Headteacher Tony Davies said parents had been reassured that their children could not be identified as only part of the thumb would be scanned.
David Clouter, who has a child at the school, said: "It's out of proportion for borrowing a book."
He added: "With the police it's very clear what they can or cannot do but with a school no-one envisaged that children would be fingerprinted."
But Mr Davies said only a few parents were still unhappy at the voluntary scheme.
He said: "When you look at the details of how this system works it is not an issue about thumb or finger prints and identity.
"We've made assurances that no-one would be able to identify a child from the scan because so little information is taken.
"The thumb scan just generates a number from three coordinates that the system recognises and this reveals how many books have been borrowed when they visit the library.
"We have spoken to parents in detail about the system and that is why those who may have been upset are not any more."
He added that the scheme was used in schools throughout Cambridgeshire.
The scheme will be phased in during the next few weeks and is expected to be fully up and running later this year.