It is the most controversial aspect of the curriculum. So perhaps it should come as no surprise that ministers sneaked out proposed sex education changes as schools broke up last term with barely a word, just before the parliamentary recess. Indeed, there is no mention at all of sex education in the cursory three-paragraph press release, or the letter from schools minister Nick Gibb that the Government used to announce its review of PSHE.
But this reticence may go deeper than a mere reluctance to talk in public about people's private parts. The bare, rude fact is that the review remit contains something much more embarrassing than sex. Buried within it is another Coalition education policy that its critics could characterise as a U-turn.
Back in the dog days of the last Labour government in April 2010, there were bitter recriminations as legislation that would have made it compulsory for primary as well as secondary schools to provide sex education was lost in pre-election "wash-up" horse-trading. The then schools secretary Ed Balls blamed the Conservatives, saying they had denied many pupils "proper and balanced sex and relationships education".
The Tories hit back, accusing Mr Balls of "petulance" and saying they supported the compulsory sex education provided that parents retained the right to withdraw their children. The Liberal Democrats also argued that scrapping the idea of statutory sex education from the age of five would be detrimental for society as a whole. Today, both parties are in power and have a chance to act in accordance with their words. But instead their PSHE review remit states that the Government "has no plans to change the law on sex education". It will remain optional in primaries.
The omission has left many who have noticed it deeply unhappy. Chris Waterman, an author and commentator on education legislation, said: "This is a most unwelcome U-turn. It compounds the abolition of the advisory group on teenage pregnancy."
Significant changes to sex education are proposed in the review, with more emphasis on teaching about relationships, the importance of positive parenting and sexual consent. But the failure to extend it to all primaries is viewed as a big missed opportunity by sexual health charities.
Simon Blake, chief executive of one such organisation, Brook, said: "It is disappointing that this has been closed down before the consultation started. It is important to keep children safe. If they don't know that you a have a penis or a vagina, or that they should ask for help if someone touches them, then we are doing them a disservice. They will learn about sex, but in a confused way."
Legally, primaries do not have to provide sex education at all, providing they clearly state their policy. For some campaigners, religious leaders, governors and heads that is a good thing. Hundreds of them wrote a letter last year claiming compulsory sex education would undermine parents' rights to bring children up in accordance with their own values.
But in 2010, Ofsted found that primary pupils needed more knowledge and better understanding of sex and relationships, and that some felt their parents did not have the necessary knowledge or were too embarrassed to ask them.
Sexual health charities stress that the education they are suggesting for primary children must be "age appropriate". "It will cover things like friendship, body parts and, later on, puberty," said Guy Slade, parliamentary officer for the Terrence Higgins Trust. "It shouldn't contain explicit sexual content."
But they are concerned that if primaries are allowed to avoid providing it at all, pupils will suffer. "A lot of children now start puberty at primary school," said Mr Blake. "It is unacceptable that they should do that without knowing what it is."
On the subject of sex education, the Department for Education's PSHE review is considering how to simplify statutory guidance. And it wants to strengthen the priority given to:
- teaching about relationships;
- the importance of positive parenting;
- teaching pupils about sexual consent.