The verdict, by two teaching unions, comes as police investigate an alleged serious assault on a 15-year-old schoolgirl. Aspiring model Danielle Price was treated in hospital for facial injuries after allegedly being attacked by another girl at Llangatwg comprehensive near Neath last week.

As TES Cymru went to press, police were still deciding whether to bring charges in the incident, apparently sparked by jealousy.

Every school in Wales now has a statutory requirement to draw up an anti-bullying policy. But Iwan Guy, acting director for the National Association of Head Teachers Cymru, said the paper guidelines were ineffective without greater sanctions.

At present heads can suspend a pupil for five days while agencies are contacted and inquiries made. It is rare for a pupil accused of bullying to be expelled.

Mr Guy said: “A longer cooling-off period is needed, as are more sanctions to deal with bullies.”

In a recent study by Cardiff university of 147 anti-bullying policies, a third of Welsh secondary schools were criticised for having strategies which were not up to scratch. Many policies were said to lack clear procedures.

But Geraint Davies, Welsh secretary of teachers’ union the NASUWT Cymru, said: “Violence in schools has reached a new dimension. No longer can a minor scuffle be disregarded - police must be brought in to deal with incidents of actual bodily harm.”

An Assembly spokesperson confirmed officials had received an anti-bullying policy by Llangatwg comprehensive that had yet to be reviewed by Cardiff university.

Jane Davidson, minister for education and lifelong learning, has promised a crackdown on bullying following a spate of incidents across Britain.