As many as one in 10 secondary pupils may be driven to find new schools because of aggressive sexual bullying.

Research due to be presented yesterday at a major conference on sex education suggests there is a growing problem with “hidden mobility”, as pupils transfer schools within the same local area.

Much of this is the result of persistent slander, with girls in particularbeing labelled as “slags” or “bitches”, according to Dr Neil Duncan, a sociologist of education from the University of Wolverhampton.

“A lot of the bullying has a sexualised and gendered motive behind it,” he said this week. “Pretty much all the insults you have from adolescents show this.

“I’ve been trying to establish why so many girls seem to disappear from secondary schools and I found a substantial human traffic of young people, particularly girls, moving from one school to another, locally. Some schools have 45 per cent mobility of this sort.

“Girls that I’ve interviewed have moved three or four times. I’m expecting to find that between 5 and 10 per cent of pupils have moved schools because of bullying.”

The conference, at London University’s Institute of Education, was also due to hear from Dr Emma Renold at the University of Cardiff, who said that sexual bullying now begins in primary school, with boys and girls using sex-related insults to reinforce “gender norms”.

Dr Duncan believes that the increasingly sexualised nature of identity in society is part of the problem. Even pre-adolescent girls, he said, are encouraged to adopt sexualised approaches to the world.

He said the sexual nature of the bullying made it difficult for girls to confide in adults.

“It is hard enough to talk about ordinary bullying, but even more so about something that slanders your own fragile sexual identity,” he said.

He has found that the perpetrators are often the most popular girls, playground “celebrities”, who are aggressive, loud and violent. Two new books, Values in sex education by J Mark Halstead amp; Michael J Reiss, and Silenced sexualities by Professor Debbie Epstein, were launched at the conference.

Silenced sexualities says that homosexuality is systematically excluded from discussion in school and argues that government sex education guidance leaves teachers feeling nervous as they try to square the emphasis on marriage with the knowledge that many of their pupils come from non-conventional homes.

Professor Epstein, who is about to move from Goldsmiths College to Cardiff University, also believes that universities are far less welcoming to gay and lesbian students than might be supposed, with many students feeling the only way to cope is to join an overt gay “scene”.

Gillian Hilton from Middlesex University was due to say that boys are left unimpressed by programmes of sex education, which do not address many issues.

Rebekah Willett, a research student at the institute who conducted a study of internet chat rooms, has found girls confidently negotiate cyberspace, chasing boys and adopting assumed identities, despite parental fears.