Parents, broadcasters and media regulators must do more to protect children from the “erosion of childhood” through exposure to adult themes and bad language, school leaders claim.

The NAHT heads’ union will today launch a charter calling for agencies to work together and recognise their shared responsibility for keeping sexual or violent media content away from young people.

The union’s annual conference in Birmingham will also discuss concerns about the use of “inappropriate” language on television before the 9pm watershed.

A survey, commissioned to coincide with the launch of the charter, reveals that 95 per cent of parents are worried about their child witnessing inappropriate material. Over four-fifths (83 per cent) were of the view that childhood is under threat, largely due to young people’s early exposure to adult themes.

A massive 96 per cent of respondents were of the view that bad language and depictions of sexual or violent behaviour were currently being screened before the watershed, with 90 per cent calling for greater regulation of programmes televised before 9pm.

Ahead of the conference, Amanda Hulme, head teacher of Claypool Primary School in Bolton, Lancashire, hit out at current shows for using inappropriate language before the watershed, such as reality TV shows Benefits Street and Secret Eaters, which have recently featured phrases such as “bloody hell” and “piss off”.

“I think it’s completely inappropriate,” Ms Hulme said. “If I used either of those phrases in school, in assembly or in front of a group of children, there would be serious repercussions to that, and rightly so. That’s as it should be. I do think that as well as parents and school leaders [having] a duty of care towards children, so [does the] wider community, which includes media providers and media regulators as well.”

Ms Hulme also criticised soap opera Emmerdale for a recent storyline in which a character tried to get pregnant to avoid going to prison.

“At half past seven? It’s just not on. I worry about the erosion of childhood. Children should be playing and having fun, and not having to worry about content that, as adults, we maybe need to think about.”

She added that there was still “work to do in terms of educating parents”. The survey also revealed that just 34 per cent had installed parental controls on devices that can access television programmes or stream material from the internet.

At the union’s conference at the International Conventional Centre today, NAHT president Gail Larkin (pictured) will also criticise recent comments from business secretary Vince Cable hitting out at the quality of careers advice in schools. “The underlying problem is, of course, that most teachers, particularly in the secondary sector, are graduates. They know nothing about the world of work,” he said.

“What an ignorant and crass statement,” Ms Larkin will tell the conference. “The current government has demolished the careers guidance service in our schools, withdrawn funding and he has the audacity to blame teachers.

“The teaching force in our schools comes from a wide variety of backgrounds and many are excellent careers advisors in their own right. Many are coming into the profession after careers in a wide variety of businesses and professions and bring with them a wealth of knowledge and skills. Once again, our colleagues are being made the scapegoats for government policies which are failing the students, teachers and leaders in our schools.”