By Katherine Sellgren
BBC News education reporter in Bournemouth
Parents too often encourage their children to behave badly at school by giving endless excuses for their behaviour, head teachers have said.
Delegates said the number of pupils with no respect for teachers was growing
The National Association of Head Teachers said parents had responsibilities as well as rights.
At its annual conference, it voted unanimously to work with the government to enforce a "respect agenda" and reduce harassment of school staff.
It also voted to improve support for pupils with behaviour disorders.
Delegates at the conference in Bournemouth said teachers and heads had a right not to be spat at, sworn at, harassed or blackmailed.
David Gray, a former head teacher, said there was a growing number of pupils with no respect for teachers.
He said soap operas and the humiliation of participants in reality television shows had played their part in eroding respect for others.
"It's the meltdown of our society's civilised values," he told the conference.
And he raised concerns about the "dysfunctional upbringing being inflicted on children", where discipline was not enforced.
Martyn Fry, a delegate from Gloucestershire, said teachers mattered as well as pupils.
"The government must support heads in dealing with the pupils and the parents who abuse and harass teachers."
Mr Fry said well-behaved pupils who were eager to learn also had educational rights.
Dr Rona Tutt, former president of the NAHT, said the authorities were often reluctant to accept the word of head teachers over disruptive pupils.
"The extreme end of behaviour has not had the attention it deserves," she told delegates.
The association voted unanimously to urge government and local authorities to review the support they offer to school leaders over violent behaviour.
The NAHT also called for better specialist provision for pupils with serious behavioural disorders who were being educated in mainstream schools.
Clarissa Williams, head teacher of Tolworth Girls' School in Surbiton, Kingston-upon-Thames, said the government had had excellent intentions towards these children and had spent money to close the gap between the "haves" and the "have-nots".
But she said more must be done to help some of society's most vulnerable children who had been "rejected all their lives".
Mrs Williams said changes to the rules on exclusions would only lead to a rise in permanent exclusions.
From September, schools will have to provide 25 hours of education to all children on short-term exclusions from the sixth day of their suspension.
"Unless schools get more resources, we will be forced to exclude permanently our most damaged and potentially most damaging young people," said Mrs Williams.
"Some of our children are so badly damaged by their life experiences that we cannot contain them."