ONE of the things you need to know if you’re the parent of a girl, or a boy, is that sex probably isn’t practised in the way that it was when you were a kid. It’s not that young people are having more of it – many studies, in fact, suggest that they are having less sexual intercourse. But what they are doing, the order in which they are coming to it and how they feel about it, is profoundly different from how it was when today’s parents were young.

This is a world in which porn is omnipresent and social media is a minefield; where young women are expected to look “hot”, and girls are often badgered by boys to send nude selfies. It’s also a world in which many girls report being cajoled or coerced into a range of sexual practices.

These shifts have been documented in a remarkable and extensively researched book by American journalist Peggy Orenstein, titled Girls & Sex. Frank and frequently shocking, it pulls no punches, and has triggered soul-searching and demands for more sex education across the United States.

Orenstein began researching the book when her daughter was 10 years old and she realised how soon she would be hitting adolescence and panicked. Previously she had written a book, Cinderella Ate My Daughter, about the “princess industrial complex” of marketing to young girls, and she had come to believe that: “When little girls play at ‘sexy’ before they understand the word, they learn that sex is a performance rather than a felt experience.” She was convinced that this seemingly innocent culture was priming little girls “for something more insidious later on”.

So she quietly began talking to girls in the United States, collecting the thoughts and stories of over 70 young women aged 15-20. (Although few of those younger than the age of consent – which ranges from 16 to 18 in the US – had had sexual intercourse, she felt even activities such as kissing and touching shouldn't be ignored within an exploration of the ethics of consent.)

It would be several years before she would decide to reveal what she was working on to her daughter. Then, one day, she said: “Do you know what I’m writing about?” Her daughter said: “No”.

“Well,” she said, “I’m writing a book on girls and sex.”

When her daughter responded that she thought this was a good idea, Orenstein weighed in with a choice fact. “Did you know that a lot of girls don’t know what a clitoris is and that its only purpose is to make good feelings?” Her daughter looked at her for a few moments, then said: “Mom, can we stop talking about your book now?”

Nowadays, Orenstein notes that they do have a lot of conversations on the subject and that her daughter does feel free to ask her questions. One of the problems, she believes, is that we treat sex as something separate, disconnected from all the other discussion of reciprocity and ethics, around what it means to be a good, caring person. “By walling it off into this separate taboo area we deny those discussions.”

Girls & Sex is, at times, a fairly depressing read. Orenstein confesses that at certain points while writing it just wanted to “lay on the ground in the dark”.

What saddened me most about the situation that was being described that was that despite all our collective knowledge around sex and the gains of the feminist movement, both statistics and anecdotal evidence suggest that the sexual culture into which young women find themselves emerging gives little weight to female physical pleasure. “What has changed," says Orenstein, "is that girls now feel entitled to engage in sexual behaviour in a way that they didn’t previously, but they don’t necessarily feel entitled to enjoy it”.

One of the things she picks apart is the culture of empowerment. She writes: “Whereas earlier generations of media-literate, feminist-identified women saw their objectification as something to protest, today’s often see it as a personal choice … And why wouldn’t they, if 'hot' has been portrayed as compulsory, a prerequisite to a woman’s relevance, strength and independence?”

The joys that the girls she interviews describe are often of going out in a sexy outfit and being desirable, rather than actual sensual pleasure. Orenstein describes “hypersexualisation” as “the water in which girls swim”. It’s what they grow up with, and by the time they are teenagers one of their prime concerns is who is the “hottest” and how “hot” they are.

Yet while they are sold the idea that self-objectification is empowerment, young women are also “getting less and less satisfied with their body image: feeling worse and worse about themselves”, says Orenstein. One girl showed her a picture of herself wearing a little cropped top and skirt to a party, and said: “I’m proud of my body and I never feel more liberated than when I wear sexy clothes.” Minutes later, this girl was confessing that she wouldn't have worn that outfit a year earlier because she was 25lbs heavier, and “some jerky guy at the party would have called me the fat girl and that would have been bad for my mental health”.

“It’s this constant back and forth for girls,” says Orenstein, “between feeling like subjects and thinking, ‘I look great, this is great’, and then immediately feeling like objects and getting unwanted attention. Meanwhile there are all these problems: depression, body monitoring, reduced sexual satisfaction. That’s an irony. Girls who are saying that it’s empowering to self-objectify are often finding that the confidence comes off with their clothes."

Meanwhile, male pleasure still reigns. Oral sex is commonly given to, or demanded by, young men – yet it is not offered to young women with nearly the same frequency and enthusiasm. What is first, second and third “base” in sexual culture, says Orenstein, has evolved. She describes an interview in which one girl told her that first base was “kissing”, second a “hand job”, and third “oral” – though only for the boy. “Girls don’t get oral sex,” said the young woman. “Not unless you’re in a long-term relationship.”

Most of the young people she spoke to did not define fellatio as sex, and considered it a safe practice – though it comes with its own risks of STD transmission. “Oral sex,” says one of the interviewees in her book, “is like money or some kind of currency. It’s how you make friends with the popular guys ... I guess it’s more impersonal than sex, so people are like, ‘It’s no big deal.’”

Another told her: “Sometimes a girl will give a guy a blow job at the end of the night because she doesn’t want to have sex with him and he expects to be satisfied.” Orenstein observed that she was frequently hearing tales of boys who understood that they shouldn’t push for or force young women into intercourse, yet seemed to think that oral sex was outside those rules. The coercion would often come in the form of just a shoulder push downwards.

Conscious that these young women are highly equality-minded in other areas of their life, Orenstein sometimes asks them: "How would you feel if every time you were alone with a guy if he kept saying, 'Would you get me a glass of water?’ You would never stand for it.”

Her book introduces the notion of “intimate justice”, created by Sara McClellan of the University of Michigan. “Just like who does the dishes in your home or who vacuums the rug, sex has a political component as well as a personal one," explains Orenstein, "and it brings up these issues of economic disparity and equality. What you have to ask is who feels entitled to engage, who feels entitled to enjoy, who is the primary beneficiary in the experience, and how does each partner define 'good enough'?”

Orenstein is good at teasing out the contradictions in how younger and older women relate to their bodies. For instance, she observes that, according to Kinsey Institute research fewer than 50 per cent of teenage girls masturbate, and when she raised the subject with young women they often said that they didn’t need to because they “had their boyfriend to do that”.

“That’s the same guy,” she observes, “who has no idea what he’s doing and is just rummaging around in there like he’s looking for a set of keys.”

Orenstein cites a recent study which showed that 50 per cent of British women could not identify the vagina on a medical diagram. One of the problems, she believes, is that we are still so silent around female genitals. “Even the fact that we call it the vagina not the vulva, is a symptom of this. We perform a psychological clitoroidectomy on girls where we don’t name their parts: we name baby boys' body parts, we don’t name girls'.”

The ubiquity of online porn has been a "game-changer, believes Orenstein. “Now, with the click of a mouse,” she says, “any child can get to anything they can imagine and a lot of things that you wish they wouldn’t be able to imagine.” One of the biggest problems, she believes, is that young people are learning about sex through porn. A National Union of Students survey found that 60 per cent of British college students said that they used porn as part of sex education. What they are using as their primer, then, is sex that frequently performs to a certain pattern and features humiliation of women: spitting on them, coercion, anal sex.

The incidence of anal sex in porn has risen steadily in recent years, so that nowadays 60 per cent of the most-looked at porn on the most popular websites, includes it. The practice of anal sex among young people has also risen. A study, by the London School of Hygiene and Tropical Medicine, of attitudes to and experiences of anal sex among British 16-18 year olds, found that female experience of anal heterosex tended to be that it was “painful, risky and coercive”, while young men described being expected to persuade or coerce reluctant partners. The main reason cited for engaging in the act was that boys “wanted to copy what they saw in pornography”.

“Again,” Orenstein says, “it was about porn and the appearance or performance of sexuality, rather than intimacy and reciprocity.”

It’s partly for this reason, Orenstein believes, that what is needed is more education. “We may think that somehow we’re protecting kids by not educating them – but then they’re going online and they’re being educated in the worst possible place where women’s sexuality is just there as a performance for men.”

Her book offers two solutions. The first is a form of sex education that revolves less around the dangers or risks of sex and more around the responsibilities, and the possible joys and pleasures of it. She has witnessed the power of such an approach through watching courses run by Charis Denison, a “youth advocate” who travels to high schools across California and with the aid of a puppet vulva, talks to young people about how the clitoris works, consent, personal responsibility, and how to think about situations that might arise at a party or club. Denison, says Orenstein, is trying to help young people “make as many choices as possible that end in joy and honour, rather than shame and regret”.

Her other suggestion is that British and American parents should follow the example of their counterparts in the Netherlands, where sex is discussed far more openly in the family context. Studies, she notes, have shown that one of the difference between Dutch teens and American teens is the way that their parents talk to them. “Americans, and this is really true of Brits as well,” says Orenstein, “frame the conversation entirely in terms of risk and danger. Whereas the Dutch talk about balancing responsibility and joy. That’s such a different framework.”

Knowing this even altered the way she spoke to her own daughter. “Up until I researched this I probably would have talked to her about contraception, disease prevention and consent. And I would have thought – job well done. But what I learned was the difference between talking about sex as risk and danger, and talking about it as responsibility and joy. It really shifted my whole thinking."

Much of the discussion around young people today, risks becoming too panicked, too prone to see only the problems, rather than the gains, of this generation. And despite the gloomy statistics and anecdotes, Orenstein is optimistic for this young generation, many of whom are already activists attempting to change the culture. “The thing I loved about them all,” she says, “is that they seemed so much smarter than I was. They were so thoughtful, and so engaged and so informed. They really wanted to wrestle with these issues.

"I think in certain ways they have a kind of awareness and savviness and entitlement that I didn’t have. They feel capable of making change.”

Girls & Sex is published by One World, price £9.99