Many parents believe schools should teach children about the dangers of pornography as soon as they are old enough to use the internet, a survey suggests.
It reveals that the majority of parents do not want it to be left to them alone to educate their youngsters about the controversial issue, and a large proportion think that pupils as young as five or six should be given lessons on the subject.
Russell Hobby, general secretary of the National Association of Head Teachers (NAHT), which conducted the poll, said that many young people are exposed to explicit materials online and on mobile phones, and need to know how to cope with this.
Many parents believe schools should teach children about the dangers of seeing pornography online
The survey, which questioned around 1,000 parents, found that six in ten parents are worried or very worried about their sons and daughters seeing violent or sexual material on the web.
But the poll also reveals that the majority (80%) of parents feel confident in protecting their children online.
While just over half (51%) said that pupils should not be taught about the dangers of pornography until they are teenagers, over two in five (42%) said that they should be educated as soon as they are old enough to access the internet, even if they are as young as five or six.
More than eight in ten (83%) said issues around pornography should form part of sex education lessons.
The same proportion thought that parents and schools should take joint responsibility for teaching children about the issue, with just 13% of parents saying it is the parents' job alone and four percent saying it should be left to schools.
Hobby said: "There is no place for explicit materials in the classroom or school, even in the course of teaching about their dangers, but many young people are exposed to such materials on the internet and phones.
"In the face of this young people need to know how to cope with and avoid these distorted views of relationships."
He added that it was "reassuring" to see that parents believe that schools are part of the support network for their children.
Stephen Watkins, head of Mill Field Primary School in Leeds said that schools should speak to children about explicit material in an age-appropriate manner.
He said he "would not dream" talking to young children about pornography.
"We don't talk about pornography, we do say to them if you see images of naked bodies and body parts then tell us.
"You start at a low level, it is about raising awareness that not everything that comes up on a computer screen should be there."
The NAHT is not the first group to raise concerns about access to explicit images.
Earlier this month Ofsted called for secondary school pupils to learn more about pornography, relationships, sexuality and staying safe, rather than just the "mechanics" of reproduction.
It suggested that many schools are failing to give pupils decent sex and relationships lessons, which could leave them open to sexual exploitation or inappropriate behaviour.
The findings came just weeks after a teachers' union called for pupils to be given lessons on the dangers of pornography.
The Association of Teachers and Lecturers (ATL) passed a resolution at its annual conference which warned that schools must ensure that pornography does not become seen as so normal that youngsters expect it to be part of everyday life.