Bullying should be easier to report and never ignored, say guidelines published by a head teachers' union.

And schools should consider providing assertiveness training for victims of bullying, says the report, presented on Tuesday at the National Association of Head Teachers' annual conference in Jersey.

The guidelines urge head teachers to set up firm disciplinary procedures against bullying and to be seen to take the problem seriously.

"Investigations into bullying incidents should be thorough and involve both the bully and the bullied," said the union's general secretary, David Hart.

"Bullying is a serious problem which needs to be eliminated. Heads have the major responsibility to take measures to prevent bullying among pupils and among staff."

Warning signs

The union advises head teachers that schools should have a clear, written policy for preventing the growth of bullying, setting out how the school would take action.

There is also a wide definition of what should be interpreted as bullying - taking in physical and verbal attacks, racism, sexism and anything in which a pupil is emotionally harassed by others - in an attempt to encourage victims to feel that they can report any difficulties.

Many bullying victims do not inform teachers, and the guidelines identify the warning signs, such as children becoming withdrawn, losing possessions and becoming easily distressed.