Most English teachers will be familiar with Anne Hathaway by Carol Ann Duffy. It's the poem that imagines the sex life of Shakespeare from the perspective of his eponymous missus.
According to Ms Duffy's sonnet, the bard very much rocked the bedposts - conjuring, no less, "a spinning world of forests, castles, torchlight, clifftops, seas where we would dive for pearls". Now, much as I like Shakespeare, the thought of him in flagrante delicto creeps me out a bit, largely because he was bald and is dead. But for rather different reasons, the idea creeps the kids out a lot more - which, of course, makes this poem brilliant fun to teach.
As it dawns on them that the rather lovely-sounding metaphors are sexual ones, their horror begins to mount, peaking around the time you suggest that the line "we would dive for pearls" is a none-too-thinly veiled reference to cunnilingus. Whichever school you teach this at, and however you phrase it, you will hear gasping, giggling and intimations of puzzled disbelief.
You dismiss the class knowing that the kids will never see Shakespeare in the same light again, and that they will never forget the poem. You will also have learnt quite a lot about the real sexual attitudes of secondary school kids.
It is true that Britain has the highest rate of teenage pregnancy in Europe, and the second highest of major global nations after the US. It is true that there appears to be an ever-growing STD problem among teenagers. It is also true that the Government and large parts of the media paint today's teenagers as highly sexualised and sexually sophisticated people.
But the truth is that being on the front line of teaching reveals a very different story. I am yet to meet a 15 or 16-year-old who has told me what cognac they like with their cunnilingus when reading Anne Hathaway, and I seriously doubt I ever will.
Sex education - or rather, the reaction of kids to sex education - consolidates this point further. It is completely natural that humans get excited when discovering things they don't know, or having gaps in their knowledge filled, and this is precisely why the atmosphere in a sex ed lesson tends to be excitable and shrieky, rather than one of louche insouciance. Of course there are kids "doing it" to varying degrees, but for a lot of them their sexual experience amounts to watching an episode of Skins.
The woman in our school who is in charge of the students' medical welfare (and who is an absolute hero) told me a couple of weeks ago that a Year 8 boy came to see her, complaining of feeling faint and sick. Having gone through the usual causes with him, she discovered he had both skipped breakfast and seen a picture of a vagina in sex education. I have no idea which one caused his ailment, but I imagine it will be some time before he skips breakfast or looks at a vagina again.
Another colleague once told me she overheard the mother of all catfights from her office window between two Year 11 girls. Having dragged them to her office, where they continued to behave like contestants on The Jeremy Kyle Show, she asked wearily, "OK, which one of you slept with the other's boyfriend?"
They both stopped dead and looked at her in horror. "No, Miss," said girl A haughtily, "but she (girl B) snogged him." They were so insulted at having their virtue questioned they both stalked off in outraged unity, boy forgotten - at least for the moment.
Interestingly, a recent study by the Christian Institute suggested that sex education might be a source of moral bankruptcy in young people, criticising "inappropriate" and "explicit" materials being shown to children as young as five, sex being compared to skipping, and the fact that secondary school children are being made aware of shockers like masturbation, oral sex and bisexuality.
However, the argument that teaching sex leads to sex is about as grounded as claiming that not teaching about masturbation would lead to a swift decline in the practice among teenage boys.
The point is that society changes. Standards change, morals change, so, of course, teenagers and their behaviours change. But are they any more sophisticated when it comes to sex than they - which is to say, we - once were?
If everybody casts their minds back to when they were teenagers, they will remember what they said they were doing and what they were actually doing were two very different things. And that will never change.
Chloe Combi teaches at a comprehensive in London.