08/12/2015 12:28 GMT | Updated 08/12/2016 05:12 GMT

The Playground Guide to Puberty and Sex (Freely Available to All Children Over Four)

Here are some gems my nine-year-old daughter recently heard in the playground.

1. Girls have vaginas, boys have peanuts.

2. Periods are when you bleed out your butt-hole.

3. Babies come out of a man's willy.

4. Sanitary towels are for mopping up spilt coffee.

Number one is kind of cute. Number two...not so much. Number three...I can sort of see where they're coming from. And number four...totally left field. Though sanitary towels might be good for that I guess.

Whatever way you look at them, they're all wrong.

And these are just a sample of the rumours bouncing around the playground. Her class, since Year Four, have become increasingly fascinated, almost obsessed, with bodies and sex. She says the boys favourite game is 'humping' (pumping the air with their groins), while the girls huddle in corners to debate whether sex really is just kissing.

My daughter is the odd one out. She sighs and goes off to play on the Trim Trail instead. There's no excitement, no mystery, no intrigue in these conversations for her. She knows the word penis . She knows that babies come out your vagina (unless you have a caesarean), and so do periods. She knows that sanitary towels are one way to absorb the blood, tampons another, or that you might even choose to use a Moon Cup.

But she also knows better than to share her knowledge. If their mum and dads have chosen not to tell them, I've warned her, best not go there: She could get into trouble for telling the truth.

I chose to be wide open about puberty and sex with her (and her big brother) right from the start. I first told them about it in simple terms when they were toddlers, revisiting, building on and widening their understanding over the years. Because I wanted them to see sex as a normal, natural, positive part of grown-up life. Not a dirty secret.

I can still clearly remember when I first heard about 'it', age 10, from my best friend Louise at school. We were sitting on a radiator behind the door of the girls' toilets hiding from the dinner ladies. I was shocked to the core. And it left a perplexing, unpleasant image of sex in my mind for a long time, tinged with the smell of wee and disinfectant.

I didn't want a similar OMG moment for my children. I didn't want my children to be able to remember a time when they didn't know.

But I know I'm out on a limb.

Despite all the evidence that shows that early sex education leads to later loss of virginity, a lower rate of teenage pregnancy, safer sex, more respectful sex and healthier relationships, are we still not, basically, a nation of prudes in this matter?

The reasons parents give for not spilling the beans vary slightly, sure.

Category A say they will talk to their children about it but they are waiting until they ask questions, because that will show they're 'ready' to know. Imagine if we applied this to the rest of education: timestables, Tudor history, how to wipe your bottom properly... Would it be better to wait for the child to initiate? "Mummy, I was just wondering, when do you use a capital letter?"

Category B let themselves off the hook by saying they've made books on puberty and sex 'available' to their children. I picture them slipping them in brown paper bags under their children's bedroom doors. Books are really, really useful, but surely not a substitute for parental explanation, discussion, reassurance. In fact, some of the books for younger children can be utterly misleading without an adult interpreter. Take Mummy Laid an Egg, for example. It's very entertaining but the wording skirts mind-bogglingly around the edges:

Daddy has seeds in seed pods outside his body.

(Sounds like some sort of exotic plant.)

Daddy also has a tube. The tube goes into mummy's tummy through a littte hole.

(Got that kids? All clear?)

When it's ready, out pops the baby.

(I wish!)

Category C sweep it under the carpet and wait and rely on school to do it for them. But school sex education in this country, despite all the debate, is still too little, too late, too clinical, too vague.

My sister Molly worked as a SRE (Sex and Relationships Education) trainer in primary schools for seven years. She said the most common resistance she encountered from teachers and parents was that they wanted to keep their children "innocent": Was it really necessary for them to know this stuff yet? they asked.

"Ignorance is not the same as innocence" became her catchphrase. Children don't stop being child-like and innocent because they are properly informed about sex. There's nothing very sweet about the bleeding butt-hole conversation.

I think I like the honesty of Category D best: those who simply say: I can't do it, I'm uncomfortable with it, it's embarrassing. Although the only response must surely be: Feel the fear and do it anyway.

Because if you don't, the playground will do it for you and it's going to be a grubby, muddled mess of misinformation. Much weirder and probably more embarrassing than the truth.

Whoops. Just knocked over my coffee...I'm going to go and grab a Maxi Super (without wings) from the bathroom.

Claire Potter is the author of a book on fussy eating and a book of quirky activities to do with children.She blogs at The Quirky Parent.