On a good day, you wouldn’t find me midweek in the Tivoli cinema in Tiverton, a blue Slush Puppie in one hand and a large packet of Maltesers in the other, watching the movie Angus, Thongs and Perfect Snogging, with children aged 11, 14 and 15.

But, having two of my own, I was quite keen to enter the mindset of the modern British teenager. Plus, it wasn’t a good day. It had been raining continuously for six weeks, we don’t have a television and I would have quite happily watched a 90-minute Gordon Brown speech about cavity-wall insulation and loft lagging, such was my craving for external stimulus.

So that you don’t have to go through what I went through: Snogging (as we shall call it for short) is all that its title suggests - a teen flick that manages to include every cliché about ugly ducklings, naughty schoolgirls, growing up, first kisses and so on. I watched it in mounting disbelief. Why? Because the film seemed to be suggesting that girls of my daughter’s age were after boys and wore tarty heels and thongs.

One girl was in year 10 (but looked about 24) and was referred to throughout as “Slaggy Lindsay”. Another 14-year-old went out on a date during the school week without wearing a bra, but protesting: “I’m notta scrubba!” I emerged from the cinema reeling. (There was a particularly gruesome “happy” ending that suggested parents should throw their children black-tie parties with boybands to make things better.)

On leaving, I remarked to my children that although Snogging was almost as unpleasant an experience for me as going to Abercrombie & Fitch with them (and that’s saying something - it’s like being mugged in a nightclub), at least now I had a dim idea what their age group was up to. I then went on to make a pointed remark about how expensive birthday parties might take place on celluloid, but not in my lifetime.

My teenagers glanced at each other, and sighed as they do when any grown-up makes a lame attempt to get down with the kids.

“No, Mum, you have no idea,” my year 10, London-day-school daughter said, and then she did the thing where she raises her eyebrows by only about three protons but still manages to convey commanding heights of scorn. “That film was, like, incredibly babyish. It was gay. We’re way . . . maturer than that.”

At this point I must explain: “gay”, as used by the younger generation, does not mean “full of the joys of spring” or “homo-sexual”; it means “rubbish”. Or at least it does for the moment. I should also explain that if you aren’t a member of the younger generation you cannot use the word “gay” to mean “rubbish” because, well, you just can’t.

What you can do is go to the new government website www.gotateenager.org.uk , an addition to the Parentline family of helplines, and quietly read the online dictionary of “teenglish”. But you must never utter a word of teenglish yourself, not even as a last resort to avoid knife crime. Do not assume you can avoid becoming a victim, and needing counselling, by asking the young male in the hoodie if he is planning to go “cotching” in his “crib”. Trust me on this.

Anyway, so when my daughter told me that Snogging - to me almost Neronian in its decadence - was in fact a Disneyfied version of modern British teendom, I felt a bit faint. It was very clear that - like many parents, it appears - I hadn’t a clue about what my children, and other children their age, were up to.

The clues are definitely out there, however. Channel 4, for instance, is in the middle of a new series called The Sex Education Show. In the first episode, the presenter, Anna Richardson, goes to a school and asks teenagers to describe pornographic sites they’ve viewed on the internet; a men’s football team are asked to drop their shorts and measure their own tackle; schoolgirls inspect pictures of differently shaped breasts; and young men discuss whether sexy lingerie or a Brazilian wax makes any difference one way or another (answer: not really).

As one tabloid reported the following day: “The media regulator Ofcom confirmed that it would investigate the programme, in which teenagers were seen describing depraved sex acts they had seen on the internet, before shocked parents were shown the vile footage from the web.” There was the usual harrumphing about whether we need to have this stuff on the television at 8pm. Then again, it’s clear to me that children don’t exactly relish the birds-and-the-bees conversation with their “rents” (teenglish for “parents”).

Phillip Hodson, the psychotherapist and author of What Kids Really Want to Know About Sex, tells me: “Yes, we are a little more comfortable with some prejudices [race, sexual prefs], but sex education has to be new-minted for each generation. Often embarrassment precludes any transmitting of conversations down the generations.”

So programmes such as this perform a necessary public service. Yes, I know that Hollywood and the entertainment industry are making a fortune off the backs of squeaky-clean promise-keepers from America’s chastity belt (one of the most successful acts in US pop music at the moment is the Jonas Brothers, a sibling rock group who have promised to remain virgins until marriage, and then there is the wholesome Hannah Montana and the innocent High School Musical).

And, yes, I know that when it comes to this stuff, it’s true that we maintain a more hands-off approach, stick our heads in the sand and hope that it will all come out in the wash.

And mostly it does. While we worry that children “nowadays” may have access to the kind of hardcore material that makes Playboy look like Play School, teenagers seem to me to be well adjusted, hard working (think of all those fantastic GCSE results) and nice to be around. The kids really are all right.

As for the fact that teens are adding online porn imagery to their experimentation, and probably engaging in slightly more risky sexual behaviour earlier as a result of the undoubtedly grisly “vile footage”, well, we can’t put that genie back into the bottle now.

As Hodson puts it: “Modern teen love at 17 knows everything and practises the repertoire of Messalina” - for those of you who aren’t classicists, the Roman empress whose name was a byword for full-on, anything-goes sexuality.

Well, I can’t say I haven’t been warned.

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