Pete and the self-styled Hot Bitch began texting almost immediately and, on his last night in Surfers Paradise, Pete asked her over to the rented apartment he was sharing with mates. For a while they hung out together with his friends, drinking. Then the talk turned to sex. "We started asking the girls there how many guys they'd ever had sex with," Pete says. "This girl said a number in the 20s. I didn't really care, but my room-mates were like, 'Dude, don't go there; she's a slut.' "

Nevertheless, the two had sex that night. After returning to their respective homes in Sydney, Pete and Hot Bitch had sex many more times, but never again in person. Despite living within a half-hour drive of each other, all their sex following that initial Schoolies Week encounter took place virtually. It consisted mostly of an exchange of sexy texts (she sent very explicit messages, Pete says, and I can confirm that the one he shares with me is blanchingly frank) and nude or semi-nude selfies.

Through the exchange of these various data, the teen couple got each other off. "She asked me over to her place heaps of times," says Pete, "but whereas before, you would have to meet them, now you can just Snapchat them and swap photos and stuff."

Welcome to the world of teenage dating, where the photo-sharing app Snapchat is the facilitator of seduction, and where mutual sexual attraction doesn't necessarily equate to sexual intercourse - in the conventional sense. It is a world in which the immediacy of social media lends an artificial intimacy to an encounter that is brokered by technology. And yet when it comes to "slutty" girls and "sexually heroic" boys, old-fashioned judgements persist.

Pete is tall and athletic, and was fresh out of high school when I met him for the first time earlier this year. He has a reputation for being a "slayer", but it seems he doesn't do as much slaying as he does accepting the overtures of the young women who pursue him. He is worldly in some ways, but not in others. He has slept with 13 girls and has 463 nude pictures on his phone, but when we meet at a cafe in Manly, his first words to me are, "I've never had a coffee before." I tell him he can have any kind of drink he likes and he orders a chocolate milkshake.

Hot Bitch is just one of many partners Pete has had virtual and, occasionally, real sex with. At the cafe, he describes his courtship routine: meet a girl out at a club and either sleep with her that night, or get her number. Then he "friends" the girl on Facebook and/or adds her to his contact list on Snapchat, a smartphone application which allows you to send a photograph that self-destructs in 1 to 10 seconds, depending on the user's settings. (Snapchat is supposedly ideal for the exchange of erotic pictures, although its ephemeral nature is easy to circumvent. Pete explains that there is another app you can load on top of Snapchat, called Snapsave, which saves the photos permanently without the knowledge of the sender.)

Usually the interaction will start with harmless chat, or Pete might ask if the girl wants to play "question for question". His typical opening gambit is, "Are you a virgin?" "It depends on the girl," he says. "If you don't think she's up for it, you don't ask."

Things develop from there, but Pete's chief objective is not to meet up for sex. He estimates he's had "real sex" with about half the girls who've sent him nude pictures by smartphone. Often, he will meet a girl at a club, get her number and, from there, the relationship is conducted entirely by text. "I actually don't try [for actual sex] that much," he says. "I try more to get nude pics. I'll be at home feeling pretty horny and I'll try to get all the nudes I can while I'm doing it [masturbating]," he says, adding that he stops chatting by text to them "the second I finish. I know it's a really dickhead thing to do."

Pete may stand at the more sexually successful end of the teen hook-up scale, but his experiences are not atypical. To the horror of modern parents, sexting - the sending of explicit texts, often containing erotic photos - is now a completely normal feature of the teen dating scene. "It's one more aspect of the vocabulary of a relationship for teenagers," says Professor Anne Mitchell, lead author of the National Survey of Australian Secondary Students and Sexual Health.

The survey, conducted every five years for the past 20 years, explores the sex lives of 2000 year 10, 11 and 12 students from schools across Australia. Last year, however, was the first time researchers asked students in detail about their use of social media. "We have a national reference group that steers the content of the questionnaire and they were all saying, 'You have to ask these questions,' " says Mitchell. "The influence of technology and social media is very visible, all around Australia."

The most recent survey supports this. The latest results, published in April, show that 34 per cent of the sample had experienced sexual intercourse, while the majority (69 per cent) had experienced some form of sexual activity. These numbers differed little from the previous survey but, this time, the survey asked about sexting, too. It found that the majority of the sexually active cohort reported receiving (84 per cent) and sending (72 per cent) sexually explicit text messages or sexts. "We looked at that statistic and we thought, 'Wow, that's really high,' " says Mitchell. "Then we understood that sexting is just part of a sexual relationship. It's part of courtship and part of sustaining a sexual relationship and it was something kids were managing fairly satisfactorily. Which isn't to say there aren't some hideous stories."

Such stories are the ones that make increasingly frequent headlines, exposing the fault-line between youthful indiscretion and the technology that rewards impulsiveness. Last year, The Sydney Morning Herald reported the case of two year 9 boys from the exclusive Sydney private school, Cranbrook, who'd had sex with a drunk year 8 girl at a party in the city's eastern suburbs. No one could claim this kind of incident was unique to the current generation of teens, but the presence of a third boy, who allegedly filmed the incident on his smartphone, was.

Another reported case involved a Sydney University student who was filmed, unknowingly, during consensual sex with a fellow student. The female student had no legal recourse when her sexual partner shared the photo with others, humiliating her among her peers.

All the teenagers Good Weekend spoke to for this story, despite being from different schools in different parts of Sydney, had seen a photo of a particular teenager at a music festival who impulsively took her top off, exposing her breasts, while aloft on a friend's shoulders. Her fellow festival-goers took pictures with their smartphones and the pictures quickly went viral on Facebook.

"She deleted [her] Facebook, Instagram [accounts] and just retreated from the social scene," says Richie*, a serious and intelligent year 12 student from a private school in Sydney's inner west. "Pretty much the whole of Sydney had seen that photo."

Sophie*, Nerida* and Eliza* are well acquainted with the Petes of their generation, as well as the pitfalls of social media. They are 16, sophisticated and never beyond grabbing distance from their smartphones. I meet them on a rainy day in a cafe close to their public high school in Melbourne's inner suburbs. It's the school holidays, so they're not in uniform, or rather, they're clad in the teen-girl mufti uniform of skinny jeans, Converse sneakers and long-sleeved T-shirts pulled self-consciously over their wrists.

They are long-haired and beautiful, and not just in the way that all youth is beautiful, although they are that, too. Sophie is blonde, tall and skinny, with an adolescent languor that speaks to her self-confidence. Eliza is a darker-complexioned version of the same. Nerida is petite and strikingly pretty. She talks fast and has a self-deprecating sense of humour.

After ordering frappés and milkshakes, the conversation turns to the topless festival-goer who went viral on the internet. What would once have been a fleeting moment of youthful exuberance has become a cause of lasting Facebook shame. "Oh my god, I'm trying to erase it from my memory ... it's not nice," says Nerida.

"She's just sitting on someone's shouldersand she's holding her top in her hand. You just see everyone with their iPhones out taking photos. I was just scrolling through Facebook and it popped up. It had thousands of 'Likes'. I felt so sorry for her."

Do the boys they know ask them for nude pictures? "Oh, they'll say anything to get you naked," says Eliza.

Nerida nods in earnest agreement: "They'll say it's just for them."

"You don't do it, but you get asked," says Sophie. Nerida explains that girls will often send erotic or nude selfies, but not show their faces, in a bid to please the boy but protect their reputations. Despite the march of feminism and the liberating effects of technology, the concept of a girl's "reputation" - and, in particular, the ease with which damage is done to it - is still pervasive.

Nerida says that the exchange of nude pics - some boys will still send images of themselves, whether or not they're requested - "only reflects badly on the girl, not on the guy". It leads us into a discussion about a girl they know who let her partner photograph them having sex, only to have him share the picture with his mates who, in turn, shared it with their mates, and so on. "Was it sex or was it on the spit?" inquires Eliza, referring to the practice of "spit-roasting", where a girl has sex with two boys at once. There is some conjecture. "She came into class on Monday and said, 'I was on the spit on the weekend', " Sophie offers. That seems to settle it.

Despite their casual treatment of these subjects, all three girls are virgins, they tell me. They're mindful of their reputations and they're in no rush. They'd like to be in a relationship with a boy first. The girls constantly monitor their Facebook, Instagram, Snapchat and Tumblr accounts and are deft at negotiating the requests they field through these various media. In real life, they experience similar pressures felt by previous generations of young women to participate in oral sex and, specifically, give blow jobs. "If you're getting with a guy, he'll definitely ask for it," Nerida says. "You have to be quite firm: they get quite annoyed if you say no." Is there any expectation that the boy will reciprocate. "No!" is the unanimous answer.

This discussion backs up the findings of the national sexual health survey of year 10, 11 and 12 students. Forty-two per cent of the boys say they've received oral sex, compared to 37 per cent of girls. Mitchell says the popularity of oral sex rose sharply in the 1990s before levelling out, but the gender imbalance has stayed the same. The girls explain that if they give into the blow-job pressure, sometimes reputational damage can ensue, particularly if the sexual partners are not in a relationship.

What about the boys: do they carry any stigma? "No, it's like, 'Good on ya, brah!', " says Nerida.

It might have seemed like fun at the time, but the iPhone-wielding festival photographers who immortalised the topless girl on Facebook were actually breaking the law. Section 91H(2) of the NSW Crimes Act makes illegal the production, dissemination or possession of child abuse material, which is what police now call child pornography. Under its Crimes Act, Victoria has similar offences for possessing and manufacturing child pornography, as do other Australian jurisdictions. These offences would encompass pictures of the breasts of an under-age girl or, hypothetically, a sexually explicit photograph of a 14-year-old girl taken by her 15-year-old boyfriend, says Detective Inspector Michael Haddow, the head of the Child Exploitation Internet Unit, part of the NSW Sex Crimes Squad.

"The boy is in possession of child abuse material, and disseminating it, if he has sent it on to his mates," Haddow continues. "But our unit will not investigate that sort of material. It will be dealt with by a Local Area Command and usually resolved under the Young Offenders Act."

Instead, Haddow's unit investigates the sexual exploitation of children online, via the internet and telecommunications devices. His officers target paedophiles who use the internet to access children, often posing online as children themselves. Haddow says the dissemination of child abuse material is increasingly prevalent in Australia, which has one of the highest rates of internet usage in the world: "We charge two or three people a month," he says. "The internet has made it easier to get access to this sort of material and to groom and procure children. Children are being exposed to the internet at ever-younger ages and some parents aren't as familiar with it as their children are."

In March this year, US authorities uncovered an online child pornography network with more than 27,000 members worldwide, some of whom had duped Australian boys between the ages of 14 and 17 into sharing sexually explicit videos of themselves. The network's members did it by posing as good-looking girls who were the boys' own age. Haddow says his unit "isn't in the business" of charging young kids who engage in these activities, but he does have a message for them: "Don't do it, because you're not in control of it."

They are rare, but prosecutions of young consensual sexters have occurred. In 2010, a 20-year-old Sydney fast-food worker asked a 13-year-old-girl for a sexy picture of herself. She sent him a full-frontal nude, which was later found by her father, who alerted police. The man was charged with inciting a person under 16 to commit an act of indecency. He was given a good behaviour bond for 12 months. When contacted by Good Weekend for this story, the man said he'd moved on, that he now had children with his new partner and was trying to put the incident behind him. He asked that his name not be published.

Richie, 18, believes teenage boys bear the brunt of adults' anxiety over technology they don't understand. "I think perhaps adolescent boys have been demonised a bit," he says. "I don't think it's very often a guy would try to shame a girl."

Richie is tall, with a loping gait and a studious air. He loves the Rolling Stones, reads widely and hopes to study law at uni. He says it's not enough for a girl to be physically attractive: she must also be funny. He says he knows of kids who send and receive sexts, but they are not in his immediate "group". "The school tells us it's illegal. Everyone knows it's illegal. They tell us, 'Don't ask for it,' " he says.

Does he think technology has fundamentally changed the way teenagers relate to each other? "It's just another way for kids to go behind their parents' backs," he says. "But in another way, there's a permanent record there. In the same way that everything has changed, nothing has changed."

One of the most interesting aspects of the National Survey of Australian Secondary Students and Sexual Health was the teens' attitudes to sex education. Almost half of respondents were lukewarm about the relevance of the sex education they'd received, citing its irrelevance to their experiences, the lack of relationship advice and discussion of same-sex attraction. According to Mitchell, the teens were "a bit sick" of sex education that stuck to the physical aspects of puberty and sexually transmitted infections. "They wanted to know how you negotiate a relationship," she says.

Some sex educators have obviously spied the gap in the market. The federal government's Cybersmart website has published a cyber-leaflet called "So You Got Naked Online" and, this year, Penguin published a cyber-safety manual aimed at parents entitled Sexts, Texts And Selfies: How to Keep Your Children Safe in the Digital Space. "The perceived anonymity of the internet gives many young people a sense of bravado, allowing them to engage in behaviours they wouldn't consider in the real world," writes author Susan McLean, who deals with sexting, cyber-bullying and online grooming in her book.

Mitchell believes that parents are frightened by technology and social media because they're unfamiliar with them, which is precisely what makes these means of communications attractive to teenagers. "A lot of the moral panic is just about teenagers getting away from adults," she says. "When the bicycle became popular, there was moral panic because, all of a sudden, they could get off and away on their bikes.

"Technology is just another one of those frontiers. Kids are much more competent at it than adults and are doing things that their parents don't know about."

The next time I meet the teen girls, Nerida chimes in on the subject of parental supervision: "The only thing my mum worries about is, like, 'If you're going to give head, use a condom,' " she says. "And I'm like, 'I didn't realise that was a 'thing'. "

"It's not a 'thing', " deadpans Sophie.

The conversation again zeroes in on blow jobs and how one-way the practice is ("It's just the self-entitlement of rich teenage boys," says Sophie), the propensity of boys to ask girls for nude pictures ("The amount of times I've been asked!" says another friend) and the rumours boys will spread about girls they've slept with as well as the ones who've refused to sleep with them ("It angers me deeply that boys are so critical of girls," Sophie says).

Some of the subject matter is toe-curling, considering the girls are all in school uniform and still child-like enough to prefer frappés to coffee. But today's parents, observes Mitchell, often think that early sexualisation is synonymous with early sexual activity. "In the 20 years that we've been doing our study, the sexual world of teenagers hasn't changed that much," she says. "It's reassuring to be working in the field and know nothing dreadful has happened. Nothing that is cause for moral panic, although there have been new things."

I pay the bill and the girls pick up their schoolbags and trundle out of the café. They have homework to do and formal dresses to decide upon. They will probably spend the evening avoiding the homework while Facebook-chatting about the dresses.

When I meet Pete again recently, he has a girlfriend, Ariane*. He's working as a chef at a local hotel and plans to go to uni next year to study commerce. He no longer has any contact with Hot Bitch from Schoolies Week.

When he got together with his girlfriend three months ago, Pete deleted "about 600" pictures of other girls from his phone. "I didn't want her to go through my phone and not like me because of it," he says. "I value her more than I value those other people." He has never asked her for a nude picture and, if he receives one, "she will be covering certain parts". "I'm at the stage where the honeymoon period is wearing off," he tells me, before adding that he thinks he probably loves Ariane. "I've never had this sort of bond with a girl before," he says. "It was a shock to the system."

He reflects that all the contact he has had with girls through social media and texting have failed to prepare him for the emotional demands of real-life intimacy. "I'm struggling with a relationship, for sure," he says. He thinks he has improved, but says that when he was younger, "I was so comfortable talking to girls via text message and Snapchat, and when I got stuck in a situation where I had to make physical contact and talk to them in real life, I found it awkward ... [Talking via text meant] I could always use the excuse, 'Oh, my friend took my phone, sorry about that.' But in person, what you say is 100 per cent from you. You can't f... it up. You might just blow the whole thing. She might think you're weird. You risk losing the girl."

Does he think teens' sex lives are any different to how they were a generation ago? "You guys didn't have the technology we do," he says. "If you know what you're doing, it's a lot easier to have sex now than back then." ■

* Names have been changed.