Parents who 'abdicate responsibility' for their child's behaviour should face sanctions from schools, a teaching union has heard.
Members of the NASUWT have told its annual conference heads should crack down on those allowing their offspring to abuse teachers.
One even suggested permissive parents should face losing their child's school place.
The union passed a motion saying the 'the changing relationship' between parents and schools is 'having a detrimental impact on pupil behaviour'.
It said reports of 'extreme pupil indiscipline' - including incidents involving knives and other weapons - are on the rise.
Patrick Roach, the union's General Secretary, warned delegates in Liverpool that better support was needed for 'home-school relationships' to help combat 'youth violence'.
But Lindsay Hanger, a teacher member from Norfolk, went further to say parents must face 'consequences' for failing to support behaviour codes.
She said: 'Appropriate sanctions are needed to encourage and require parents to support the schools.'
The union passed a motion saying the 'the changing relationship' between parents and schools is 'having a detrimental impact on pupil behaviour'.
'But this is not the case in many places today...
'I think the Government needs to go further, with a strategy to ensure that all parents of school-aged children are expected to uphold the behaviour strategies or risk their child being denied their place in the classroom.'
She said while many schools ask parents to agree to support a behaviour policy, they are 'not challenged when they fail to do so'.
The parents 'abdicating responsibility' were a 'small minority', she said, but the disruption was impacting the ability of other pupils in a class to learn.
She also warned some schools are pursuing attendance goals 'at any cost' and think it is 'more important than 'safety concerns'.
Other members agreed that parents were contributing to discipline issues in schools.
Gary Upton from Buckinghamshire, said: 'It seems a lot of the behaviour from our students comes from parental behaviour.'
He added instead of being able to implement 'instant action' for swearing, now they have to go through support processes to 'appease parents'.
And he said some teachers are even having to devise strategies to 'keep violent parents outside of school reception.'
Andrew Dunkley, from Aylesbury, said parents often 'encourage their children to be defiant and refuse sanctions'.
The motion committed the union to opposing blanket 'no exclusion' policies, which some Left-wing campaigners have been advocating for.
A Department for Education spokesman said: 'The Education Secretary is committed to a comprehensive programme of behaviour support for schools.
'Our Plan for Change places a relentless focus on giving every child the best start, no matter their background, including establishing free breakfast clubs in every primary school, proven to improve behaviour, attendance, attainment, wellbeing and readiness to learn.'