Meet the squeaky clean movie teens

I don't drink, I've never smoked a cigarette in my life and I don't take drugs. I tried a drink a few years ago but it just wasn't my thing so I simply stopped. I prefer to go out clubbing without having a drink," says Harry Potter newcomer, Freddie Stroma, 22, matter-of-factly over salad at the sedate Mulholland Tennis Club in Los Angeles.

Demure not decadent, polite not pouty, sober not sloshed: a new breed of Good Boys and Girls – call them The Squeaky Cleans – is replacing Hollywood's naughty bunch. Their role models are Natalie Portman and Jodie Foster, not Lindsay or Britney. They worship culture, not cocaine, and their favourite haunts are gyms and museums, not nightclubs.

Stroma's co-star and Potter "love interest" Emma Watson, 19, echoes those sentiments: "For me, I didn't have time for that [to rebel]. I was working too hard to be the rebellious teenager, though I'm sure when I hit my 30s I'll go crazy. I'll have this rush of hormones and madness."

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She's only joking, of course, stressing her gratitude that she came of age in England rather than in the madness of Hollywood where former teen star Lindsay Lohan epitomises the dangers of growing up too fast, too young: "Don't you think I'm one of them? Don't you think I'm crazy?" she asks coyly. "No? Well, thank you. But I can totally understand why they go nuts. The level of interest in their lives and the pressure to be perfect, and they're teenagers. And that's what you do, you screw up," she muses.

When Disney-created pop band the Jonas Brothers announced last year that they had pledged to abstain from premarital sex, they were met by a flurry of ridicule and parodied at the 2008 MTV Video Music Awards by the less-than-pure Russell Brand. While today's young stars aren't exactly in a rush to follow the Jonas Brothers by going out and buying purity rings, there's undeniably a new awareness at work.

The influential Los Angeles-based talent manager Melanie Greene – who guides the careers of Gossip Girl's Ed Westwick and Paul Bettany as well as Stroma – is, for one, delighted by the change in attitude she sees in today's rising stars: "Freddie is a wonderful role model, and I personally welcome the positive new approach that he embodies. Bad behaviour is becoming less and less tolerated. For any young actor who's serious about their career, good values are important."

Hollywood's Squeaky Cleans today boast a growing membership including Kristen Stewart, 19, Dakota Fanning, 15, and Camilla Belle, 22.

Well educated, The Squeaky Cleans are smart, clean-living and moral. Career-orientated, they keep themselves busy with wholesome activities while saving themselves for the right person. They refrain from attending every opening of an envelope, instead preferring to do charity work, pray or enjoy a light, alcohol-free, supper with friends. Indeed, young Fanning even recently pledged, before her mother Joy and agent Cindy Osbrink, that she won't have a teenage pregnancy or get any tattoos or piercings, at least until she turns 18...

These actors all started young, Fanning in I Am Sam at six; Watson debuting in Harry Potter and the Philosopher's Stone, aged 11; Belle starring in A Little Princess at nine, and Stewart making her major movie debut as Jodie Foster's daughter in Panic Room, aged 11, before finding fame as Twilight's Bella.

Stroma's initiation began a little later, and when he walked up the Harry Potter and the Half-Blood Prince red carpet, he celebrated not only his screen debut but also a 2:1 BSc in neuroscience from University College London.

"Education has always been very important to me," says Stroma, who attended the Hogwarts-style Radley College, a boys' boarding school in Oxfordshire. "I enjoyed every minute there. It was a very good school with great facilities and great teaching. It was lovely and old-fashioned and they really taught their children how to be gentlemen. I was having so much fun that I rarely got homesick."

And, despite the fact he has no skeletons in his closet, after the BBC announced his casting as the Gryffindor Quidditch keeper Cormac McLaggen in the sixth installment of the Harry Potter franchise 18 months ago, Stroma eschewed Twitter, Facebook and all the usual forms of youthful social networking.

"I left Facebook after Facebook groups began appearing about me and suddenly your personal photographs start becoming public property," explains the handsome, blond, 5ft 11in actor.

"When the BBC first announced the new cast members, I hadn't even started filming and yet there were all these websites, all having something to say about me. It was very bizarre. It was mostly complimentary, but because I do a bit of modelling as well, they'd got hold of my portfolio so all those pictures got around too. Now there are message boards about me: all these people claiming to be good sources saying things that are completely inaccurate, like my parents are divorced and stuff, none of which is true.

"It's not like there's any drunken photographs out there of me, it was just more the fact that they were my photos of friends and family; suddenly, everyone could look at them."

In common with his fellow Squeaky Cleans, Stroma lives vicariously on-screen, in a world where these smart young actors can make believe all the things they refuse to do in their real lives – Belle playing the mistress of a man twice her age in her latest film, Adrift, while Fanning was seen fall-down drunk in her recent sci-fi film, Push, although she insists that's only for the camera: "I didn't actually drink for that scene. I didn't even know that I was going to do it that way until the minute I did it," she grins.

Fanning has been dubbed The Million Dollar Baby, and her co-stars already number Tom Cruise, Sean Penn and Robert De Niro. Having grown up in such an adult world, this religious girl feels no peer pressure to drink at parties or otherwise misbehave: "That's not something I think about right now and hopefully will never have to experience. I know what's right for me, and I stay on my path."

Priding herself on good behaviour, she adds: "I don't think I'm a brat although I realise that most people think that kids in the business are brats. But you don't have to be a brat to be an actress. I just enjoy it so much that there's no time to do anything like that. And why would I want to, when I'm enjoying myself? My family and friends keep me grounded. I'm a Southern Baptist, and I grew up in the south, so every Sunday I went to Sunday school and I've grown up in a family where that's really important," says the actress.

The Squeaky Cleans are all super-accomplished: Watson – who speaks French fluently – scored As in all her A-levels last year and has just enrolled for an Ivy League degree, while classically trained pianist Belle – currently dating Joe Jonas – speaks Brazilian and Portuguese, and the precocious Fanning learned to read at the tender age of two.

Belle kick-started her acting career as a child model: "When I started at nine months old I modelled in commercials but I stopped once I started doing films. Modelling has never been a career, it just kind of happened. Obviously it's fun and an honour to represent companies like Miu Miu and Vera Wang, but it's not a job. I'm not going to do something that isn't me" says sensible Belle who rejects modelling offers as often as she does party invitations: "I don't live that Hollywood life; I don't take part in it. Obviously I'll go to events but very rarely. It's usually a friend's premiere or an event where I have a relationship with a designer; it's always for a reason. I don't go out just to go out which I think makes a big difference. I'm not showing up just to show my face.

"I've been to some of those Hollywood clubs with my friends, but we just show up and we're like, 'OK, this is what it is! Great!' and then we leave... I don't even drink alcohol. It's pretty much sparkling water. I've never been a big drinker," says Belle who apparently chose Jonas when forced to make a romantic decision between Jonas and Twilight's Robert Pattinson.

Ask if it's fun being the envy of every teenage girl on the planet, she smiles serenely: "Well, I don't know, you can't help what people say or what people write. People are going to say what they want to say. I am just living my life and I'm perfectly happy," says the actress who still lives mostly with her parents despite the fact she bought her own home – 10 minutes away from them – two years ago.

Likewise Watson sees no harm in waiting. "I'm sure my knight in shining armour will come along at some point, although hopefully not too soon because I have a lot of work to get through and I don't want to be distracted," she says.

While talking with Kristen Stewart on the set of New Moon last month in Vancouver, she sighed at my suggestion that she might have anything in common with Bella, her tormented screen alter ego: "You wouldn't believe how boring I am in real life. I don't have any of the issues that Bella has. If I wake up in a bad mood, I'll go running or do some kind of physical exertion. If you completely exert yourself, you can, like, clear your mind. I don't focus on success and I'm not an impulsive person," she says. "My biggest splurge to date is buying my own home – complete with a studio where my mom can paint."

Neatly placing his knife and fork together on his salad plate, Stroma is nothing but impressed by his Potter co-stars, concluding: "There is that Hollywood scene of young stars who seem to get a lot of bad press, but Emma, Dan [Radcliffe] and Rupert [Grint] are such brilliant role models. There's simply nothing bad to report about them because they're all really lovely and they are down to earth.

"Maybe it's because they work so hard and it's been one film after the other –and they've been doing it since they were 12 or so – and they work such long days. They must have time to let loose or whatever, but they're working constantly so they grew up quick, I think. They learned how to behave themselves and I imagine they must have had good role models around them to look up to."

If Stroma's post-Potter career doesn't pan out, then he already has a back-up plan: "If my dramatic career doesn't work out, I will go on to research and find cures for Alzheimer's or Parkinson's and other motor neurone diseases. It's a very exciting field of research. But I'd like to continue in drama so it wouldn't be very smart of me if I blew this amazing opportunity with an inappropriate lifestyle."

'Harry Potter and the Half-Blood Prince' is out on 15 July