Growing pains: The National Theatre of Scotland

ONE hundred rats, says David Harrower, will cross the stage in formation. And there's a scene with a red carpet, chimes in Vicky Featherstone, and lots of costume changes. And then she catches Harrower's eye and starts giggling. I know what's going on now: I'm being taken for a ride.

But if the team behind 365 one night to learn a lifetime, the new National Theatre of Scotland production for the International Festival, are telling tall tales about how the show might look, it's probably because they don't yet know themselves. I sat in on a rehearsal less than three weeks from the first preview, and there was a tangible sense of the play being written before my eyes.

"We don't know what the end of the piece is," says Featherstone, NTS artistic director and the director of 365. Ever ebullient, it seems to me she is trying not to sound worried. So is that exciting or terrifying? "Both," says Harrower, "in equal parts." "But it doesn't feel paralysingly terrifying," says Featherstone. "It feels actively so, because we're searching."

365 is an ambitious attempt to create a piece of theatre about young people leaving the care system. With a cast of 16, 15 of whom are under 25, and programmed for the Playhouse, Edinburgh's biggest stage, it's an experiment on a monumental scale. In the rehearsal I witnessed, Featherstone was digging deep with three of the young cast, Laura McMonagle (Zoe in River City), Helen Mallon (who was in the NTS production of Tutti Frutti) and Owen Whitelaw. The cast also includes River City's Ryan Fletcher and his brother, Scott. They play a short scene and then pull it apart slowly, one stitch at a time: what is each character feeling? What is driving them?

Harrower has his script and pencil in hand. "We made it clear from the very beginning that we were going to ask a lot of people," he says. "The actors have been given a lot of responsibility for their own character." "They've been extraordinary," says Featherstone. "I am incredibly humbled by their approach, it's not usually what we ask actors to do in this country. They've been coming to David and trying to inspire him to write for them." Harrower, on the other hand, is more of a turn-up-with-the-finished-script sort of playwright. He won an Olivier Award for Blackbird, which appeared at the Festival in 2005 and has since been produced Off Broadway and at the Sydney Opera House, directed by Cate Blanchett. This way of working is new, a challenge.

"I did write some stuff and turn up on the first day with my proud sheaf of virgin pages ready to be interpreted," he says. "But we had to throw most of it away. It has been an exploration, characters have come and gone. Seeing the actors and seeing the set has been important. It's not been without its terrors."

The subject matter is a test too. The phrase "issue-based" can be the kiss of death to a play, and everyone on 365 takes pains to insist this is not an "issue" drama. But it did start with an issue. The press release even came with a page of statistics: 6,000 children in the UK leave care every year, three-quarters have no qualifications, a fifth are homeless. Half of all prisoners under 25 were in care. Ninety-five per cent of children in care have mental health problems.

By choosing to focus on the moment when young people within the care system turn 16 and find themselves thrust out into the adult world, 365 reaches out towards other issues: not only addiction, homelessness, unemployment and gang culture, but also belonging, family, and aspirations for the future.

The central metaphor for the play is the "practice flat", in reality represented by various different living arrangements, where vulnerable young people, already with more than their fair share of problems, are expected to learn overnight the lessons they need to be grown-ups. They must leave the system at 16, while the average age for leaving home in Britain is 24.

From the first night, they can be making tough decisions. "When you move into your place, there is a 'Yahoo!' period," explains Featherstone. "You're no longer surrounded by 12-year-old kids, you're 16, and your flat becomes 'the empty', the place where the party is. Kids end up being thrown out by the police or the neighbours."

She emphasised that some young people do manage the transition successfully, and was also quick to point out that the play is not intended as a comment on the shortcomings of the system. "It's more a comment on myself for not knowing it, and that I'm critical as a member of society of the way I think young people should be able to have more control of their lives. And when you look at what has happened to them, there is no way that they can have.

"If it's about anything, it's about individual characters who every day have to fight to find the resilience to even exist for the day or see a future because of the neglect that they've suffered. Is it possible for them to survive in the way that I see survival, or just in the sense of literally being alive every day? As a national theatre, we have to find the way – and this might not be it because it might not work – to ask the big questions of our day, and this is a big question for our day."

"It's very easy to get appalled and angry," Harrower says. "That's an emotion you don't want to take into a play because you'll end up preaching, or something worse. We had to talk about how we ingest the statistics and the anger and create a piece of theatre which evokes a range of emotions. It's not an illustrated lecture, it's not a piece of documentary theatre, it's got to be an emotional, visceral experience."

For all the research Harrower and Featherstone did, meeting social workers, psychiatrists and many young people, this play promises to be strikingly different to the verbatim and documentary theatre so prevalent on the Fringe this year.

There will be music (Blue Nile's Paul Buchanan has written a song that will be used in the production) and a physical theatre element (Steven Hoggett, who worked on Black Watch and The Bacchae is movement director). The scale of the production leaves room for a wide range of non-naturalistic theatrical effects – Harrower promises "flights of fancy": "The nebulous term 'realism' wouldn't even cover the area that we've been investigating. It's been like hearing fairytales. There was this kid who ran to the river, undressed and walked home to his mother, leaving his clothes by the riverbank. This is going on, that is realism."

The kernel at the heart of the play is the importance of knowing your own story. Most of us take this for granted: we can ask our parents what we were like growing up. We have photographs, memories, anecdotes. Some young people in care may have none of these things.

Harrower says: "A child psychotherapist talked to us about the kids he spoke to who didn't know their own narrative, who had no idea of the reasons for what happened to them. He said one of his jobs was to introduce their narrative back into their lives and that was such a potentially psychic shattering experience for them."

Featherstone says: "I can't believe how people can survive this, they go through worse than I could ever imagine. But they do and they're resilient and brilliant and funny. The thing about all these young people is that their stories aren't neat, every day that they survive is a new beginning for them. Actually it's all about new beginnings rather than endings."

• 365 one night to learn a lifetime is at the Playhouse, 22-25 August, 7:30pm, with a matinee 23 August, 2:30pm, as part of the International Festival.