A new survey has revealed children are spending their school time chatting online when they should be number crunching on calculators. Toby Mullins, headteacher at Seaford College, tells reporter Andy Robbins why other schools should follow his lead in blocking access to the sites.

Schoolchildren trying to duck out of work is not a new problem for teachers.

Pupils have always been masters at developing different ways to dodge their textbooks in favour of mischief.

However, a survey this week revealed more than half of youngsters aged between 13 and 17 use the internet website Facebook during lessons.

Figures released by Worthingbased IT company Global Secure Systems shows pupils spend one hour in every ten at school on the social networking site.

The company questioned 1,000 children, with 52 per cent admitting they had logged on to Facebook when they should have been working.

MPs and councillors have now called the site, as well as other social networking websites like Bebo and MySpace, to be banned from schools.

Toby Mullins, headteacher at Seaford College, agrees classrooms are for learning and not networking.

He warned one of the biggest dangers of social networking sites was their exploitation by cyberbullies who were taking their taunts online.

Mr Mullins said that in recent years bullying had moved from the playground to the internet.

He said: "As a school we have never come across any paedophiles using the networking sites but we have had instances of people being extremely unpleasant online.

"We've even had to sort things out with people from other schools as well."

The survey shows more than a quarter of students who were questioned said they spent more than half-an-hour on Facebook everyday during lessons.

However, Mr Mullins said most schools have already blocked access to social networking sites.

Seaford College took action 18 months ago after staff became aware of pupils using Bebo when they should have been learning.

He said: "As far as I am concerned a school's computer system is for academic use only. We have got a very big and strong firewall to prohibit people accessing certain sites.

"We never saw this phenomenon coming but I don't think anyone did.

"With modern technology, though, it is easy to set up a screening process and stop people accessing these sites in school."

Now that it is denied in the classroom, Mr Mullins said the biggest problem was when children were at home.

He warned many teenagers were turning up for school weary from tapping away at their computer keyboards into the early hours.

The headteacher wants parents to monitor their children's internet use and stop them from spending hours in chatrooms and on networking sites.

He said: "I believe the evenings, when pupils should be doing homework, are the real challenge. I have spoken to other headteachers and we all agree the challenge is how to stop youngsters from spending hours on these sites.

"The big worry as a headteacher is that kids are staying inside, sitting at computers, rather than being outside playing sport and keeping active.

"It is all very well harping on about a time gone by and a different age but we need to stop our children spending all their time on these sites."

Mr Mullins said another major concern was how pupils were unaware what was happening to the information they were putting in their online profiles.

Many are adding their email addresses, telephone numbers and personal information on to their pages which can then be accessed by complete strangers.

He said: "When you put information up on Facebook it isn't yours any more. These websites make money by letting others have your information and getting yourself off is very difficult.

"By the time you are able to take details off, you don't know how many servers around the world have already stored your details."

The blight of Facebook has even spread from schools into the workplace.

Earlier this year it was estimated the popularity of social networking sites was costing British businesses almost £6.5 million in lost productivity annually.

Mr Mullins said he had spoken with staff at other schools who had revealed several horror stories about former pupils coming unstuck through their Facebook pages.

He said: "I spoke to someone from one school who said they had an old boy come back for a visit. He told them he had missed out on a high-profile job because the company had looked at his Facebook page and then decided he wasn't the man for them.

"Pupils have to be made aware that these websites are like a public record.

"They must make sure that what they have got online is the sort of thing they would be happy for anyone to see because you never know what it will be used for in the future."

Mr Mullins said he was not against social networking sites in principle. Seaford College allows its pupils, including many boarders and foreign students, to access networking sites using school computers as a cheap and reliable way of communicating with their parents.

However, he urged parents to keep a keen eye on their children's internet use so they didn't become sucked into an almost constant online existence.

He said: "It is not all bad news but, as adults, we have to get to grips with it.

"Facebook and sites like it are the tip of an iceberg we need to identify."