CHILDREN'S SUMMER SPECIAL / Taking the X-factor out of sex: Do we need books to teach children about sex? When they start asking tricky questions, and everyone feels embarrassed, is an upfront approach the right one?

FOR A long time Babette Cole couldn't work out how people had babies, given that people only have two legs. 'I grew up around animals, and I saw them having sex constantly,' she says; 'it didn't seem to me something that human beings could possibly do.' So when Tom Maschler of Jonathan Cape suggested that she might like to write an entertaining sex education book - 'he wanted lots of animals bonking' - she declined. 'I have a stud farm, and I see those horses doing it the same way all the time. It really is very dull.'

But then Cole got to thinking that there might be a place for a book which showed what people did. Mummy Laid An Egg], her 28th picture book, consequently has illustrations of 'some of the ways mummies and daddies fit together': on surfboards, highwires, dangling from balloons over mountains, bouncing about gleefully on space hoppers - extravagant children's interpretations making a serious point about sex being fun.

This effort to demonstrate that shortage of legs is no impediment to reproduction has not been greeted with unqualified enthusiasm. Helen Paiba of the Children's Bookshop in North London thinks 'the biggest, and probably most appropriate market for this book will be 18-year-olds.' But Mummy Laid An Egg] looks as if it is well on the way to becoming as popular with small children as Babette Cole's Princess Cinders, the story of the dungareed princess who only wants to get rid of her pesky suitors and be a Ms. The new book inverts convention in a similar sort of way: the parents are clueless, and go pink when they find out how babies are really made; the children already know everything. The pony-tailed dad suggests brightly that 'sometimes you just find babies under stones'; the earth-mother mum that 'you just squidge them out of tubes'.

Sugar and spice and all things nice make their traditional appearance; so does a topical delivery by dinosaur. Children find this sort of silliness on the part of adults very gratifying: my two gave the impression that it bore out everything they had always thought. They both said the book was funny, and didn't mention its educational aspect. When pressed, the nine-year-old said: 'Oh yeah, well, I already know all that stuff', while the six-year-old (much more the age group at which the book is aimed) just said 'mmn' and wandered off, either uninterested, or else unwilling to reveal his private thoughts.

Sex education books give children and parents a way of broaching The Subject, and can usefully be put down and picked up again later, so that if a child says 'mmn' in a way that you don't quite understand, it doesn't matter. But since sex involves emotions and values, and is deeply embarrassing to some people, gauging the tone of a book so that it is instructive but not shocking is obviously extremely difficult. 'Normally my books take about half an hour to write,' Cole says; 'this one took three months. And where usually I use three sheets of layout paper, this time I used a whole pad.' Mummy Laid An Egg] deserves to succeed, because it has a proper story with a beginning, middle and end, and makes sex look full of fun and variety. As Cole herself says, 'it has a nice attitude'.

By contrast, Peter Mayle's rather po-faced Where Did I Come From? (Pan pounds 5.99) tells us that 'the man wants to get as close to the woman as he can, because he's feeling very loving to her. And to get really close the best thing he can do is lie on top of her and put his penis inside her.' No doubt this seemed the simplest explanation, and, possibly, it is what most people do most of the time, but at this crucial moment, we hear only what the man feels (nothing about the woman wanting to get close) and it's implied that men invariably get on top and do all the active stuff.

Mayle does, however, use the words 'penis' and 'vagina'. Louise O'Connor, who trains teachers in sex education at the Froebel Institute in London, believes that 'using the proper words right from the start is quite important, otherwise you're sending a message that this is something a bit peculiar. And it could be quite confusing.' Babette Cole opts for 'tubes' and 'holes', partly, she says, because these are descriptive terms, and partly because 'penis and vagina are not very nice-sounding, and are difficult to spell. I felt these rather unpleasanty words would hold up the flow.'

A recent survey found that 96 per cent of parents wanted their children to receive sex education at school, largely because they find it so difficult to address themselves. This is out of ignorance as well as embarrassment; they fear they may know less than their children. Michele Elliott of the charity Kidscape says she hears 'groups of 13-year-olds talking freely about oral sex, which I didn't even know existed until I got married'.

Ideally, parents should talk to children about sex 'from a very young age', according to Alison Hadley of Brook Advisory Centres: 'Very often when children ask questions at six or seven they don't get answers, which sends a double message. They fabricate what they don't understand, and they come to think this is not a nice thing to talk about.' Michele Elliott has heard six and seven-year-olds earnestly explaining to each other that 'you swallow this stuff, and then a flower comes out of your bellybutton'. And Alison Hadley thinks many adolescents are hardly less ignorant: 'We see surprisingly high levels of confusion among young people. The assumption is that teenagers know everything, because sex is all over the media, but there are huge gaps in their knowledge: they ask if you can get pregnant if you are still a virgin, or if you get into a bath in which a boy has ejaculated.'

Even for those parents who are committed to proper sex education, and are not constrained by embarrassment, pitching the information correctly can be problematic. I sat down enthusiastically to Tell All at the very first hint of a question; within two minutes my daughter had wandered off, bored. Louise O'Connor also describes how she 'told (her) six-year-old and three-year-old everything. They came to me a bit later and said: 'Mummy, we've done it, and Tanya still hasn't had a baby.' '

Some members of Christians in Education - a group lobbying to allow parents to remove their children from sex education classes in schools - would find this shocking: they disapprove of teenagers being shown how to use condoms. And Sukey Firth encountered similar reactions from her health visitor when she used How a Baby is Made by Per Holm Knudsen (Piccolo pounds 2.99) to help explain an imminent new baby to her two-year-old son. 'It's a great book, and it has this wonderful bit in it that says: 'To show his love, the man puts his penis inside the woman's vagina, they hold each other tightly and move together happily.' My health visitor seemed to think Gus and his friends would start moving together happily. It seemed rather an odd thing to be concerned about.'

This just shows how carefully you have to sift sex education books, if you want one which reflects your own attitudes. There will, for instance, probably be a limited though no doubt grateful market for Who Made Me? by Malcolm and Meryl Doney (HarperCollins, pounds 4.99) which claims in its foreword: 'The question 'Where do babies come from?' cannot be answered simply with a scientific explanation. God, love, marriage and families must be included if children are to get a true picture.' Since this book implies that only married people make love, most soap operas could become very puzzling to its young readers; it could also be quite upsetting for children who are the result of some more temporary liaison.

Helen Paiba says there is a consistent demand from parents for sex education books at all levels: new baby books for small chidren, puberty books, frank and fearless books. Mummy Laid An Egg] is a welcome addition to the genre, avoiding the usual patronising earnestness: it's entertainment, rather than a parable or textbook. It is not to everyone's taste, no doubt, but nor are any of these books. The truth is that sex education books can only ever be a backup; certainly, as children get older, any discussion of sex has to involve some assertion of values, some sense of emotion. And if you want to communicate your own values, and your own emotions, you have to talk.