It involves anal sex as a matter of course. It can include images of women being choked or gagged. It is not uncommon for it to feature an ambiguous version of consent, in which "no" can mean "that sounds like fun".
And yet pornography is increasingly serving as a substitute for adequate sex education, new research has found.
Researchers Maree Crabbe and David Corlett conducted 140 interviews internationally, with pupils, teachers and professionals from the porn industry, and presented their findings in London last week. On average, they said, most pupils will watch porn for the first time at the age of 11.
"Definitely, a lot of what I know about sex is because of porn," one teenage boy told the research team.
"Growing up, watching porn - that's sort of where you get your grasp of what's normal and what's not," another added.
Girls, meanwhile, tended to be shown porn by male friends. "Most of the stuff that guys show to girls is, like, joke stuff," one girl said. "Like girls having sex with horses or whatever."
The researchers argue that the failure of sex education to address the positive aspects of sex drives pupils to seek further explanation in porn.
"Discussion of sex and intimacy is too often avoided in schools," the Australian researchers said, presenting their findings at a conference at London University's Institute of Education this week. "Porn has become a cultural mediator in how young people are understanding and experiencing sex. Porn is our most prominent sex educator."
And the sex education community admits there is truth in these findings. Mary Clegg (pictured, right), chair of the British Association of Sexual Educators, confirms this. "A lot of our sex education is based on a don't-do model," she said. "But young people are hungry for more explicit information. They're curious and they're hormone-driven."
Porn, meanwhile, is freely available on the internet. This has affected what teenagers understand as normal. "You think, shit, look at his dick," one boy said of male porn stars. "I can't compare to that ... My dick can't compare to anyone else's."
Pupils similarly assume that practices such as anal sex and ejaculation in women's faces are a normal part of any sexual encounter. "The first time I had sex, I decided to go anal," one boy said. "She didn't like that."
The researchers reported that 88 per cent of scenes in porn films show physical aggression, such as choking, gagging or spanking. This aggression is overwhelmingly directed at female performers. Nonetheless, the women always appear to enjoy the experience.
"Some guys have this perception that, if they just do it anyway, it'll be amazing," one teenage girl said. "They just try and slip it in the other hole. It's not really about asking any more - it's all about doing and hoping for the best."
"You want to grab her hair and pull it back," a male interviewee added. "I mean, it's a turn-on."
Acknowledging the difficulty of preventing access to porn, the researchers suggested that sex education lessons should therefore equip teenagers with the skills necessary to evaluate what they see.
"To be unable to critique imagery is equivalent to being illiterate in the modern world," they said. "We need to help young people to resist peer-group pressure to consume porn or to respond to partners' requests for sex they've seen in porn."
Mrs Clegg, meanwhile, calls for more open classroom discussions about sex and arousal. "Just giving them information about the potential they have for pleasure means they've got to work at it a bit," she said. "That means being in a loving relationship rather than trying out what they've seen in films."
Exercises for teachers to use in sex education lessons:
Teenagers are presented with a series of practices - deepthroating; ejaculating over a woman's face; giving pleasure to men; giving pleasure to women - and asked to categorise them as belonging in the "porn world", the "real world", neither or both. There are no right or wrong answers: the idea is to generate discussion.
Finish the story
Pupils are given a series of scenarios and asked to suggest possible outcomes. For example, a boy is at his friend's house and his friend suggests watching porn. He does not want to stay: what should he do, and how?