Cheltenham Ladies’ College is blocking its pupils’ access to such sites after finding that boys at other schools were logging on to rate girls according to their looks.

Even Daniel Radcliffe, star of the Harry Potter films, has been teased on a mock profile apparently posted by fellow pupils.

Liz Carnell, director of Bullying Online, receives about 20 complaints a week.

“The comments left on the victims’ blogs cause alarm and distress. They can amount to harassment, which is a criminal offence,” she said.

Some messages go beyond the abusive. “One girl was told that her web stalker wanted to kill her. The consequences of such bullying can be far-reaching,” Carnell said.

One site, which claims to carry postings from 10,000 British children grouped under the names of their schools, encourages users to put up photographs and to list their friends and their favourite music and drinks in the style of celebrity magazines. Friends and strangers can then post comments.

Michael Birch, co-founder of the site which is based in San Francisco, said that he had turned down requests from four British schools to have their names removed from the site. He had no intention of trying to filter out bullying comments.

He said that teenagers could screen out messages from unwelcome visitors. “If people want to be nasty to one another, if they are looking for a medium to do that, they are just as likely to do it through this network as any other,” he said.

“You can’t physically hurt anyone on the social network website, but if you bully someone in the playground you can hit them. It’s just people saying nasty things about other people, there’s nothing physical going on. You could argue it is safer than the real world.”

For most children the blogs are a way of showing off holiday snaps or clothes, but a 15-year-old pupil at St Helen and St Katharine, an independent girls’ school in Abingdon, Oxfordshire, was sent the message “U r sooooooooo ugly!” by an American girl who had seen her picture.

The school now advises pupils not to put pictures on the website and has blocked it from school computers. One member of staff described it as “lethal”.

On the website for the independent City of London school for boys, a profile of Radcliffe appears to have been posted by a fellow pupil. It includes the words “friends: none” and “[the] media’s sucking **** **** and you still deny u like punk and wear tartan trousers. When u coming back anyway?? suppose u dont need education when ur as rich as u r”.

One entry from Ranelagh Church of England school in Bracknell, Berkshire, last week read: “Thought I would repeat how much everyone hates you and that my lifetime wish is for you to [be partly] sliced into pieces.”

In another example — in northwest England — a boy posted on his school’s intranet pictures of his former girlfriend with her head superimposed on a pornographic image. Although the school found the perpetrator and removed the photographs, the girl and her family felt that the damage had already been done to her self-esteem.

The boy who was bullied because of his musical talent is one of the most striking recent examples.

He described how “one boy took photos on a digital camera of me being bullied. I was in the form room and three or four boys would be pushing me about, dragging me over or throwing me on the desk.

“It was like a form of happy slapping. But then the boy posted the images on his blog. I was very upset and humiliated and begged the boy to take the photos off but he just laughed.

“People saw this and judged me as a loser. The bullying is bad enough but to have it displayed to have boys make fun of me makes it far worse.”

Mervyn Brooker, headmaster of Bolton School boys’ division, said he had come across incidents of people sending bullying e-mails to blogs. “There is huge potential for bullying. They’re anonymous people and lots of people join in, sometimes with more than one name so it can look as though lots of abuse is coming from different participants,” he said.

Vicky Tuck, headmistress of Cheltenham Ladies, said that however hard schools tried to block access, it was almost impossible. “You can’t lock the gates to these sites,” she said.

Additional reporting: Sally Jones

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