The National Association of Head Teachers' (NAHT) conference, which starts today in Torquay, Devon, will hear calls for new sanctions to deal with violent mothers and fathers who prevent schools from disciplining their children.
With classroom disruption and exclusion high on the political agenda, ministers are bound to come under new pressure to give schools new powers to deal with them.
Tomorrow, delegates will argue that parents, as well as pupils, are part of the problem. A small but growing number are disrupting the work of schools and are placing both heads and staff in a vulnerable position, they will say.
Some waste teachers' time by refusing to allow their children to be kept in detention, while a few threaten violence. Others make false allegations against staff which often include suggestions that their children have been victimised.
Jenny Simpson, president of the New Forest association of the NAHT, will tell the conference that the law should be strengthened so that such parents can be called swiftly to account.
"Abuse and aggression by a few parents has a detrimental effect on the whole school community and it wastes valuable time. Its victims can often become traumatised," she told the Independent.
Binding contracts which they would have to sign before their children started school could set out both their rights and their responsibilities, Ms Simpson will argue.
The contracts, which already exist in many schools but which have no legal status, often ask parents to bring children to school regularly and on time, to support the school's discipline code and to accept its ethos. In return, the school agrees to provide a caring environment, challenging lessons and reg- ular information on the child's progress.
Rowie Shaw, the association's director of professional services, said that schools were being asked to uphold society's moral values without any legal backing. She was particularly critical of appeals panels on exclusions, which have sparked strike threats twice in the last month by returning disruptive pupils to schools.
"When the school gives a detention the parent can refuse. When the school excludes a pupil - always a last resort - the governors uphold it then three people dragged in off the street overturn it. There are a whole raft of issues about parental responsibility," she said.
Among the other issues to be raised at the conference will be the headteachers' proposed boycott of league tables for 11-year-olds. The association is asking school governors to withhold their test results so that ministers cannot publish them next spring.
Conference delegates will defend the decision, which has led to criticism that they are prepared to ask governors to break the law but not to do so themselves.