A 16-year-old girl has been released on police bail after a teenager was knocked unconscious in the latest case of the "happy slapping" craze.
Becky Smith, 16, suffered temporary paralysis after being set upon by a teenage mob.
The gang filmed the attack on their mobile phones.
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Becky, of Blackley, Greater Manchester, said of her attackers: "I think they are attention seeking. They want someone to notice them and think they are hard."
Police said a girl of 16 had been arrested on suspicion of assault.
The school, Plant Hill, has also warned parents that children were downloading the video of British hostage Ken Bigley being beheaded in Iraq onto their mobile phones.
A Government-backed task force is to be set up to advise on how to improve the behaviour of children.
Its job will be to formulate a new national code of behaviour, setting out minimum standards expected from pupils.
It will examine new powers for headteachers to tackle violent pupils.
And it will consider how to make parents take responsibility for the way their children behave.
Education Secretary Ruth Kelly pledged to create the task force after the Prime Minister said he was determined to make tackling the problem a top priority.
David Hart, of the National Association of Head Teachers, said: "Heads must be given the power to apply their schools' zero tolerance policies without bureaucratic interference.
"Parents must accept the consequences of their own violent or aggressive behaviour, even if it means the exclusion of their own children."
Secondary Heads Association general secretary John Dunford said: "Schools cannot impact on behaviour without the support of parents and the wider community and the group will need to work in this context."
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