Systematic stigmatising - or “mobbing” as it is known in Germany and Scandinavia - is less violent but almost as detrimental to a child’s self confidence as overt bullying, and it is more likely to lead to clinical depression. Barely studied by experts, it forms a huge invisible part of the bullying iceberg in countries where violent aggression is less of a problem.

Surveys in Germany show that only 8 per cent of primary pupils are subject to physical bullying, teasing and name-calling compared with about 15 per cent as a worldwide average and up to 24 per cent in Britain.

However, in a surveyof 15,000 children in the state of Lower Saxony, up to 20 per cent were victims of mobbing. Only one in three victims of mobbing tells a teacher with only one in two informing their parents. Many psychologists believe mobbing should be taken as seriously as violent bullying.

The term comes from Norway where it is used to describe group aggression in birds. It is likely to involve a group of children ganging up on an individual and subjecting them to humiliation or exclusion - to the extent of ostracising them from school events and lying about them to classmates and teachers. It is seen as a systematic stigmatising process which grinds pupils down psychologically. The results can be severe depression over long periods.