The education secretary, Ruth Kelly, is facing pressure today to make sex education compulsory after an Ofsted report condemned current provision as "poor".
Schools are failing to provide young people with appropriate sex and health education as well as a whole raft of skills designed to equip them for adulthood, Ofsted said.
Family planning campaigners immediately called on the government to make sex education compulsory.
Ofsted found that personal, social and health education (PSHE) classes too often teach teenagers the facts instead of an understanding of how to deal with situations. In sex education, for example, they might learn about the types of contraception available, but not how to negotiate sex and relationships.
Other schools were failing to teach the lessons at all, opting to fill the curriculum with academic classes. Still more were piling the now-compulsory teaching of citizenship into lessons, leaving not enough time to properly get to grips with PSHE.
The single biggest problem was the lack of trained staff, with classes seen as an add-on and directed by form teachers rather than specialists, the report from the schools' watchdog said, adding that there had been little improvement since its last report on the matter in 2002.
The classes are also supposed to prepare school leavers for the world of work, and provide them with work experience and career guidance.
The Family Planning Association called on ministers to make teaching PSHE a legal requirement from primary school onwards.
Anne Weyman, FPA chief executive, said: "This report makes for worrying reading, but sadly confirms what we have known for some time."
Jan Barlow, chief executive of sexual health charity Brook, also called for sex education to be compulsory.
"By making it a compulsory part of the national curriculum, delivered by specially trained teachers, the government would send out a clear message about its importance.
"Children need to start learning about sex and relationships from an early age, so that they get used to talking about feelings and relationships."
Questions have been raised about the stance Ms Kelly will take on sex education because of her devout Catholic beliefs. She has denied reports that she would turn down a ministerial job in the health department because she would not want to legislate on controversial issues such as contraception and abortion.
The Ofsted report recommends that better training for individual teachers be introduced, schools should design a full programme which tackles difficult issues such as mental health issues and better monitoring of pupils' progress should be put in place.
David Bell, the chief inspector of schools, said: "I do not condone any schools deciding not to teach PSHE. Schools need to concentrate on ensuring that those teaching PSHE have the skills and support they need to deliver a first class programme of lessons."
"Good PSHE lessons should provide opportunities for pupils to reflect on their own attitudes and values as well as those of others. But today's report found that far too little assessment is undertaken of the standards achieved and progression made by pupils studying PSHE and, even where it is present, it is often poor."
A spokeswoman for the Department for Education and Skills said officials were developing materials for tests in the subject to address the fact that there was very little monitoring of pupils' progress.
"PSHE is widely taught in schools in England, and we continue to improve the effectiveness of what is taught by providing clear guidance and support to teachers."
She said the government had provided extra cash to increase the number of specialist teachers. "Over 5,000 teachers are set to benefit from additional training in the next two years."
