Teens on shows such as The OC and Smallville don't look anything like the high school kids I see squeezing themselves into the train on a Monday morning at Eagle Junction. And with good reason.

When Tom Welling was cast as a 15-year-old Clark Kent on Smallville he was actually aged 24. I'm sorry, but when Welling is striding around Smallville High he looks less like a school kid and more like my optometrist.

Then there's actor Benjamin McKenzie, who was 26 when cast as the 16-year-old brooding Ryan on The OC. Charisma Carpenter was 29 when cast as 16-year-old Cordelia on Buffy. Scott Wolf was 26 when he played 17-year-old Bailey Salinger on Party of Five. And Sabrina the Teenage Witch (Melissa Joan Hart) would be more at home on the set of Teachers considering the actress is in her 20s.

Watch repeats of Beverly Hills 90210 and you'll see Dylan McKay (Luke Perry) - one of the first teenagers I've seen with a receding hairline. Actually, Perry was 25 playing 18. And it's a wonder 90210 didn't do a "I wonder if I should freeze my eggs?" episode featuring Andrea since Gabrielle Carteris was a spritely 34-years-old when she played the school nerd.

And don't for a second go thinking that "faux-teening" is a new phenomenon. Bung Grease in your VCR and you'll realise that Rydell High was more like an adult community college. When this movie about a group of high school kids was filmed in 1978, Olivia Newton-John (Sandy) was 29, John Travolta (Danny) was a more youthful 24, but Stockard Channing was a ridiculous 34 when she played Rizzo.

So the question is, why aren't genuine pimply, gangly, awkward teenagers being cast as teenagers? Answer: because teenagers are often pimply, gangly and awkward. And aren't able to spout pithy Oscar Wilde lines on demand. Hollywood explains away its mutton-as-lamb casting by claiming that teens don't want to see themselves on TV the way they really are. It's "aspirational" casting, apparently. But I disagree.

Aspirational - scmaspirational. I love the creation of a neologism that is so positive, a real buzzword, to justify what is a marketing strategy. Why wouldn't teenagers want to see themselves? Because they are led to believe that their lives (and they) are uninteresting. Adults do 'teen' better than teens themselves. Youthfulness is yet again a commodity to be bought and sold, not a legitimate stage of life.

The American way is to cast older people as younger people, elide the age difference and naturalise the behaviours which are really the way adults imagine (through market research, anecdotes and observation) that teens behave and the problems they encounter. Adult actors are also less likely to cause conflict on set or be beset by the same problems these programs exaggerate in the name of entertainment. If you can convince the audience these actors are young, then they are commercially a better proposition.

The upshot of this is that these highly articulate, zit-free TV "faux-teens" (who all seem to pose for FHM in their spare time) leave real teenagers feeling insecure and inadequate. Using adults to represent teens is another way in which so many popular culture forms accelerate maturation for the target audience and leave them with a sense that their own stage of life is somehow invalid and boring. It can potentially instil in young people the desire to 'grow up' - especially through aesthetic means. Sadly, this can be readily achieved these days but while a young person in the 'real' world might look older, they don't always have the cognitive skills to match, unlike their televisual counterparts - and that's highly problematic.