Stereotyping boys as either testosterone-fuelled delinquents or emasculated weaklings does nothing to help them to develop a positive sense of their own masculinity, says the Family Planning Association.
Now, in a move to promote better sex education for boys, it has published a manual for those running training programmes for teachers who venture into this often "scary territory".
It says they should confront their own prejudices about masculinity before they can train teachers to help boys challenge society's masculine stereotype: to hide their feelings, disregard their health and have sex often.
The results of conforming to this stereotype, says the manual, Moving Goalposts, are reflected in rising levels of sexually-transmitted infections, high numbers of teenage pregnancies and a massive increase in HIV infection rates, particularly among young gay men.
Although work with boys and young men is now a key part of the Government's Teenage Pregnancy Strategy, boys are often sidelined in current sex education, it points out. Boys see it as "women's business" - and it is often provided by women.
Fathers rarely tell their sons about sex, and boys see school sex education as "too little, too late and too biological," says the manual. ("It is all about fallopialies (sic) and periods," one young man said.) The manual's authors, Simon Blake, director of the Sex Eduation Forum and Max Biddulph, a lecturer at Nottingham University, say that what boys really want is "a man who is able to talk casually and candidly about issues such as uncontrollable erections in the school corridor or biology lesson".
But they also stress that, while they want to see more men recruited as sex educators, boys need positive female role models, too.
"What boys say is they don't mind which sex the teacher is, what matters is that they know their stuff," Mr Blake told the TES. He added that a male and female teacher working in partnership could often prove very effective. Both single-sex and mixed groups were valuable for sex education, Mr Blake said: single-sex groups to convey basic information and explore attitudes, and then joint groups for discussion.
The manual recommends several techniques for creating a safe and unthreatening environment in which sex, relationships and masculinity can be explored with boys. They include developing working agreements on behaviour, using "icebreaker games" to start each session and employing ing distancing techniques such as role-playing and make-believe scenarios.
It also advises teachers to remember the "just in case" rule: providing information even if young men claim to know the answer. Often they pretend to know when they don't, it says.
Moving Goalposts can be obtained from fpa direct, PO Box 1078, East Oxford DO, Oxfordshire OX4 6JE, tel. 01865 719418, price pound;14.99 plus pound;2.50 p amp; p.