A SCHOOL in Willesden has defended using pupils' biometric data - converting fingerprints into pin numbers to process school lunch payments.

Capital City Academy , in Doyle Gardens, Willesden, is using the controversial system in place of swipe cards to save time identifying pupils when they buy their lunch or during registration.

Children place their thumb on a glass screen which picks out four points of their thumbprint and converts it into an identifying code.

A spokeswoman for the school said there was no way the code could be converted back into the image of the print and matched up to a police data base.

The school was criticised by angry parents last year after it introduced the system but failed to ask for their permission.

The school was then forced to consult the parents and the choice to opt out was offered. If a child does not wish to have their fingerprint taken they can be given a four-digit pin code, but this has to be remembered and cannot be changed.

The Information Commissioner's Office, which promotes public access to official information, said it was not illegal for schools to collect pupils' fingerprints without their parents' consent.

About 60 per cent of children at the school now use the biometric system and Alex Thomas, principal of Capital City Academy, said it has been very successful.

He said: "Many parents, once they have seen the system in action, have supported the school in introducing the system.

"Previously students were using cards, which could be lost or stolen. The biometric system prevents that happening and is much quicker."

It also meant children did not have to walk around school with money, which reduced potential bullying. Parents could top up their accounts online.

It is believed around 80 schools in the UK are now using the biometric system.