'How was school?" As every parent knows, this question is usually met by a grunt and "Why haven't you bought the biscuits I like?" Then later on they accuse you of not being interested in what they do all day.

This week was different. My youngest came in outraged. "Today was the most disgusting day ever. Our teacher showed us pornography."

The "porn" in question was a film of a woman giving birth, part of my daughter's sex education. It was, she said, the most revolting thing she had ever seen. "Really?" I asked, because we watch Embarrassing Bodies together. Like many a young girl or indeed sensible woman she had decided not to have a baby unless it was a kitten and certainly not THAT way.

But at 12 she certainly knows what actual porn is. The boys at school have it on their phones. Talk to any primary school teacher and they will tell you this has been an issue for some time.

The latest summit, then, on how to stop this awfulness has been another "damp squib". Its chair Maria Millerpromised she would "throw down the gauntlet to companies such as Google, Facebook, Microsoft and Twitter". These companies should do more to block access to porn via parental controls, and block images of child abuse outright. This, like chocolate oranges at tills, used to be one of David Cameron's big issues also. But it wasn't big enough for him to show up at the summit.

So Miller, not surprisingly, did not throw down any gauntlet, a) because she is Maria Miller and – apart from squeaking "as a mother" every so often – appears clueless, and b) because her job is impossible. She is Secretary of State for Culture, Media and Sport and also Minister for Women and Equalities. This is the buy one, get one free cabinet post. And what are "Equalities" when they are at home?

She is concerned about images of child abuse online. Well who isn't? Who defends them? The fact is that an image of child abuse is an image of a rape, a crime that is already illegal. You can't make it more illegal.

The easy access to hardcore porn is indeed problematic. Typing "internet porn summit" into a search engine, I got to "sumi pussy licking sluts". My typing is awful. But porn is ubiquitous and hardcore torture porn is everywhere – and no it's not Fifty Shades of Grey. It's blood, vomit and faeces.

Even the softcore stuff presents us with the "new normal". A nice 14-year-old boy I know told his mum when he was going on his first date (the girl was 13) that he was taking a condom to be sensible "for the anal".

The young feminists who, understandably, say they don't want their viewing censored by the state remain somewhat bamboozled by the happy-hooker mythology that recasts sex work as just another choice but tends to forget the trafficked woman locked up 16 hours a day, and the porn stars who are extremely damaged before they get into the industry and are even more damaged when they come out.

The punters' websites which review prostitutes or porn also promulgate the idea that the women basically love their job and it's just another choice, though one few punters would want their wives making.

As for the state taking on the internet, it's a joke. The free market wants commodities that sell and nothing sells like sex or drugs. So leglislators tinker at the edges, while all forms of sex are sold online.

In such a world, just as we teach our kids how to cross the road, so we have to teach them about porn and about consent. Both of which make the Boden-loving right deeply uncomfortable. They make all of us uncomfortable, to be honest.

Mostly, though, we discuss not kids accessing porn but what images of themselves they put on social media sites. "Did you see what she put on Facebook?" "Why all the 'likes' on Instagram?" "How do you do the privacy settings?" One dithers between paranoia and laxity. What is definite, though, is that the redefinition of what is public and what is private has already happened. What happens online stays online forever. Education, not censorship, is the answer. Children are sexual beings. It's simply that late capitalism is commodifying their sexuality earlier, extending its market. But we are governed by technophobes, who, on one hand, tell us that the state via surveillance must be able to see everything and, on the other, that we must stop our children from seeing what they easily can. Even our state broadcaster the BBC has on its iPlayer a simple tick box to confirm you are over 18.

To admit we can't control what our kids see online is hard. But show me a parent who hasn't used the internet as a babysitter (as we used to use TV) and I will show you a liar.

Those most vulnerable are those who do not know their way round the online environment, not those posting pictures of their toddlers. Google will not protect your child, any more than the government. We have to teach our kids about the worst aspects of the internet and of sex. Both involve consent. In order to do this we have to trust our children. Are we grown up enough to do that?

• Comments on this article will be switched on on Thursday morning.