There’s no holding back in the rehearsal room, with talk of sex, incest porn and bondage. One musical number has a chorus about masturbating. It is funny, revealing and deeply troubling. The play, Why Is the Sky Blue? (Or How to Make Slime), is based on interviews with 10,000 people aged between six and 22, about the effects of pornography on their lives. Its title comes from the children’s search-engine questions, which included “Am I gay?” and “How big is my penis?”

The cast members are drawn from the same age group as the interviewees and the show includes songs, verbatim experiences and improvised conversations. One of the young people says that, after stumbling across pornography online: “I didn’t even want to look at my own [genitals]. I was scared after watching.” Another comments: “It has affected my mental health and the way I feel about myself, the way I speak to girls.”

Tackroom Theatre worked with schools, theatres and the charity Barnardo’s to conduct the largest piece of research ever undertaken on the subject. As well as the play, which runs for three weeks at London’s Southwark Playhouse in London, there will be a website and educational material.

“It’s been a really long-held ambition of mine to do this,” says the director, Abbey Wright. “We wanted to attempt to track the influence of porn from when people first see it, sometimes around six or seven, to when they’re first entering into adult relationships.” The main challenges of working with performers who are so young have been regarding what is age-appropriate. “It gets to three o’clock and you really ought to rehearse an explicit song but there’s a seven-year-old who hasn’t been picked up yet,” Wright says. The younger children wear noise-cancelling headphones during the more explicit content.

In rehearsals, two actors are having a conversation about what sort of porn they watch; one of them smiles and looks embarrassed. These aren’t scripted, and come from the actors’ own experiences. “We are put in quite a vulnerable position but I think the way we feel comfortable with it is we still have our own boundaries,” says one of the actors, 20-year-old Zachary Hing. “We know what we’re comfortable saying on that night. If there are circumstances or if one night someone is in the audience that we don’t want to share things with, we have that freedom to go: ‘I’m not going to reveal these things.’ When I’m talking about racism or transphobia, it doesn’t necessarily feel like I’m sharing something personal but it feels like I’m talking about a wider social issue.”

Hing, who is British Chinese and a trans man, says he welcomes being “given a professional platform to say these things to a live audience. I think it’s a problem that a lot of people within ethnic minorities or the queer community feel, but we don’t have the courage to say it out loud because when we do we get shut down or we’re accused of being oversensitive. For me, this play is important because we’re being given that chance to talk about [porn] openly. I don’t feel like I’m exposed, it feels quite liberating for me.”

Eleven years ago, Wright was working with young offenders. “I observed the extent to which pornography was shaping the way they thought about themselves and relationships,” she says. “I saw kids who were quite disturbed and confused by it and then I saw kids who completely accepted it, but in a way that I felt made them quite disconnected from themselves. I found it quite sad.” She wanted to create a project “which would have a genuine impact nationally. We started talking to children and asking about their experience, and realised children’s voices had to be the centre of the piece.”

Numerous things shocked her during the research. She asked a group of six and seven-year-olds if they had seen anything inappropriate online and “the majority of children [I saw] have seen pornography and will describe it to you. I find it shocking that the experience of these very little children has not come to light.”

It emerged that sexting was prevalent in the first two years of secondary school. “A group of 12-year-old girls in Edinburgh were saying: ‘I guess it’s flattering but I don’t really think they should be sending me a dick pic because I’m only 12.’ Then it shocked me how many young people I met, most of them boys, who described themselves as currently being, or previously having been, addicted to pornography.” One 14-year-old girl told her: “I have had guys who assume that [things they’ve seen in porn] are OK to do to me without even asking.”

Wright also says there are the “ambiguous aspects” to porn. “I meet a lot of young queer people who talk about how queer porn isn’t necessarily a great representation of queer identity, but at least it’s something,” she says. When LGBT sexuality is rarely discussed sex education classes, porn becomes educational for many young people. “I’ve met young people who talk about that wonderful moment of liberation when they stop trying to force themselves to watch straight porn.”

What is most shocking to Wright is “the lack of conversation and education on the subject”. She isn’t claiming to have come up a solution to the problem of pornography, but advocates much greater education as well as providing parents and teachers with the tools to have difficult conversations. One 14-year-old girl told her: “If you put a phone in a child’s hand, you are putting porn in their hand. Don’t put a phone in a child’s hand unless you are happy to talk to them about porn.”

Wright hopes to tour a smaller version of the show and plans to do workshops with 25 theatres around the country. “There are always dangers in the world for children,” says Wright, “but somehow empowering them and giving them the tools to navigate those dangers in a very positive way seems like quite a hopeful thing.”

• Why is the Sky Blue? (Or How to Make Slime) is at Southwark Playhouse, London, until 19 May. Box office: 020 7407 0234