"Kids can get past firewalls if they are really keen and the solution to get around the ban will be sent around very quickly on mobile phones or the internet," she said. Ms Treyvaud, a consultant to the Centre for Strategic Education, said cyber bullying was an increasing problem and "not just a teenage thing", as, by grade three, most had a mobile phone, hotmail address or blog.

Secondary Schools Principals Association president Brian Burgess welcomed the move, but said reducing cyber bullying was not just a matter for schools; parents had to work with schools to tackle the practice. "If we thought that cyber bullying was going to stop just simply by banning YouTube, then we are living in fantasy land," he said. "If this was the only thing that was done then it would be a token gesture and it would be a waste of time." Experts suggest cyber bullying, which has taken over from playground bullying, accounts for almost 90 per cent of school abuse. A Mission Australia National Youth survey released last year revealed 30 per cent of respondents worried about bullying or emotional abuse.

Last year, a DVD of a 17-year-old girl being bullied, assaulted and humiliated by a gang of 12 youths was widely viewed in segments on YouTube. It showed youths urinating on the girl and setting her hair alight. Ms Allan said schools had been told to update anti-bullying policies by year's end. She said schools had been blocking access to selected websites identified by the Education Department since October 2006. Filters tracked words and sequences.

McKinnon Secondary College blocked access to video-sharing websites last year. Assistant principal Andrew Newton said, while he was not aware of cyber-bullying incidents at the school, the move was pre-emptive. He said the school banned video-sharing sites such as MySpace and YouTube and live chat rooms. "The kids were told at assembly, and there were a few groans but they don't seem to mind too much now." At Melbourne Grammar School, headmaster Paul Sheahan said students had unrestricted access to websites, with the school advocating free speech.

"There is some good resource material on (YouTube and MySpace) and if we block access, the boarders can't get it, while day students can access it at home, so there is an issue of fairness," Mr Sheahan said. He said the school knew of the negative clips on some sites and tell parents in its newsletter. "It won't be a heavy-handed 'don't' use the sites," but parents would be reminded "not to assume that all is sweetness and light".

One student asked about the ban said it would be useless — "It will make it more popular. If there's a will, there's a way." The student, who didn't want to be identified, said it was easy to access banned sites, with firewall tips available online.