An interesting column on that whole sex-ed thing by Barbara Kay. I especially like this bit:
Human beings are the only creatures for whom shame, guilt and modesty (especially in girls) are instinctive. We are also the only creatures who assign certain behaviours to the realm of the private, and certain to the realm of the public.
Schools are by nature an artificial construct. They were designed to transmit objective knowledge about subjects that are amenable to collective learning: literacy, numeracy, history, scientific data and the arts.
Sexuality is different. When children of both sexes absorb information from a relative stranger about deeply private feelings and behaviours in a group environment — when the private is made public — they are being co-opted into a rudimentary form of collective voyeurism, which, even when earnestly accompanied by exhortations to responsibility (condoms!), is inherently titillating and a licence to breach natural modesty boundaries.