THE vast majority of teachers would fight shy of the intimate questions raised by a popular sex education course, headteachers believe.
Oral sex, the mechanics of gay sex, sexually transmitted diseases and role-playing games all feature in the scheme run by Exeter University.
Its ethos is about encouraging young people to resist pressure from the media and their peers to have sex. Rules are established banning derogatory or personal comments by pupils or teachers.
The programme is widely praised and there have only been two complaints among the 800 teachers who have been on training sessions.
But parents this week said that they should be consulted before there was classroom discussion about, for example, what semen tasted like. Margaret Morrissey, of the National Confederation of Parent Teacher Associations, said: "There are things which are not necessary, that are not essential to a good sex education programme.
"Before a question was answered, teachers would need to know from parents whether it should be answered in an open debate, or individually after class."
And David Hart, general secretary of the National Association of Head Teachers, said: "We have to draw the line somewhere, and I think most teachers would feel that answering that kind of question would be outside the realm of normal sex education."
Around 100,000 pupils a year are taking the A Pause (Added Power and Understanding in Sex Education) programme. It was established in 1990 as a small research project in two Exeter schools. It now operates in more than 150 comprehensives in 16 local authorities.
Run by the university's department of child health, the scheme sees teachers, school nurses and "peer educator" sixth-formers working together to deliver lessons and discussions for pupils.
Most work is done in Years 9 and 10. In Year 9 trained sixth-formers set up discussions with pupils on, say, the consequences of sexual involvement based on the case study of a 14-year-old girl. They also lead role-playing activities on how to resist unwelcome sexual pressure.
In Year 10, a teacher and school nurse jointly encourage pupils to discuss contraception and sexually-transmitted diseases.
Teachers on training courses are presented with a list of "challenging" questions which could be presented to them by pupils. They are also given scenarios in whichYear 10 pupils are encouraged to discuss "stopping points" before full sex, including exploring each others' bodies and oral sex.
The scheme backers include the Government's social exclusion unit and the Office for Standards in Education, which has said teenagers turn to magazines for information not available in school.
SEX TIPS FOR TEACHERS
Guidelines on sex education in schools state that:
* All schools must have an up-to-date sex and relationship education policy, drawn up by governors and head in consultation with parents.
* Parents can withdraw their child from sex education, except for the parts included in the national curriculum, such as reproduction.
* Teachers should set ground rules, such as avoiding personal questions and using the proper names for body parts.
* Explicit, inappropriate questions or those about abuse should be acknowledged and dealt with later.
* Sex education should be taught in the context of the importance of marriage or family life but recognise other "stable relationships".