“We are becoming a nation that defines itself by what it owns rather than by what it is,” said Eric Spears, head of Staplehurst primary in Kent.

Pupils pestered parents for fashionable and expensive possessions while young children with no morals were turning to theft and violent crime. “It is not that they don’t have an intellectual understanding of the difference between right and wrong. It is that they don’t care about the difference. What you can’t get by fair means you get by foul.”

Mr Spears said schools were often the last bastion of moral values, working hard to promote moral understanding yet parents sometimes did not understand their role in developing a child’s moral sense.

The behaviour of celebrities was also a poor role model. “No wonder pupils are confused by the mixed messages they get from their sports and pop heroes,” he said He said no effective way of dealing with disaffected young people had been found and that teachers trying to instil discipline had to look over their shoulders constantly because they feared pupils’ allegations of child abuse.

“Rafts of human rights legislation seem to have done little for the human rights of teachers.”

He warned against political quick-fixes saying deep-rooted behaviour problems needed a long-term commitment to resources, training and support for schools.

And Mr Spears threatened annual disputes with Government over performance pay unless ministers made the commitment to fund it properly. He said heads and governors face spiralling wage costs but inadequate budgets to fund them.

“If the comprehensive spending review does not build in some protection then the future will be one of either continuous, debilitating disputes over who is entitled to what, or increasing redundancies among staff so that schools can afford to pay those that are left,” he said.