Sex-education organisations claim that there is a place in the classroom for live-action footage of masturbation. They say that showing explicit educational videos, such as Martin Cole's 1971 film 'Growing Up', would help teenagers develop a healthy attitude towards sex.
Rebecca Findlay, of the Family Planning Association, says: "Where do young people go to get images of sex? It's normally the internet, and it's usually pornography.
"So they have unreal expectations of sex and their bodies. We need to be able to look at someone masturbating and see it not as pornography but as instructional."
She says that such images might help destroy the taboos around sex: "What is masturbation? How do you do it? What does it feel like?
"These are conversations people should be having in sex education classes.
But in British culture, sex is something embarrassing, something you laugh about, not a normal part of society."
David Evans, of the sex education scheme, Apause, agrees.
"I have no theoretical or moral objection to making those kinds of images available to schools," he says.
"But, on a pragmatic level, schools would find the whole thing too risky and probably would not allow it to run."
He believes teachers view sex education as a marginal subject, peripheral to their careers.
"It's a high-risk activity, for low professional gain," he says.
And David Limond, of Trinity College, Dublin, who has conducted research into 'Growing Up', believes that the film has stymied any rational debate around the use of such images in the classroom.
"If it was done appropriately, there's no reason why you shouldn't show the act of masturbation in a school classroom," he says. "But people aren't even prepared to view these materials. They go straight back into the bunker."