Many a classic Broadway musical was tried out in distant towns before being submitted to the merciless scrutiny of New York. But few new musicals can have played quite as many towns so quickly as Feather Boy, by the Novello award-winning composer Debbie Wiseman and the Oscar-winning lyricist Don Black.

It was commissioned by the National Theatre for Shell Connections, its nationwide festival of youth theatre. Which means that Feather Boy is currently being performed by about 25 different youth-theatre groups up and down the land before one troupe gets to stage it at the National itself next month.

“All the directors and musical directors gathered for a weekend workshop in Bath last November,” says Wiseman. “We suggested possible options for staging it, then they went off and did their own thing. Only now are Don and I seeing the results.”

“And we’ve been amazed,” Black adds. “Each director has put a totally different stamp on it.”

The group chosen to perform at the National is from Blatchington Mill, a performing-arts school in Hove. “Amazing kids,” Wiseman says. “They sing in tune, they have great voices — and no fear! They just go on stage and deliver.”

Was there a fierce scramble to get the National showcase? “It was very competitive,” Black confirms. “A lot of kids saw it as a huge opportunity to open doors.”

Every actor is under 19 — “a bit ironic, when you consider that one of the musical’s main themes is the relationship between young and old people,” Wiseman says. “It’s quite a demand on teenagers, to think themselves into a pensioner’s mind. But this lot do it well. And I never write down for kids. These songs are as tricky as anything I write for professionals.”

Feather Boy started life as a children’s novel by Nicky Singer. It was Blue Peter’s Book of the Year, no less, in 2002. Touching but also funny, it tells the story of Robert, a 12-year-old boy violently bullied at school and upset by his parents’ divorce. But when he starts to visit an old people’s home as part of a school story-telling project he meets a pair of feisty pensioners, and his life is gradually transformed.

The inexhaustibly sparky Wiseman — who, in an amazingly short time, has already written and conducted scores for more than 150 films and TV dramas — encountered Feather Boy when she supplied music for a BBC TV adaptation of it. She and Black decided it would make a good musical as well.

“So many strong themes worth singing about,” Black says. “The bullying of course. But also the business of growing old. My favourite song is called Still Me in Here, in which an old lady points out that she hasn’t changed on the inside, even if her appearance has. I think that will touch a few hearts.”

Wiseman has resisted the temptation to recycle the music she wrote for Feather Boy’s TV manifestation. “When you write a film or TV score, the music is at the service of the action. Writing a musical is different. There the songs carry the action. They are the focal point.”

The 67-year-old Black, whose 1,000-odd lyrics include five James Bond title-songs, hopes that Feather Boy can be expanded into a full-length West End musical from its present hour-long format. “One obvious strand to develop is the reason why the boy’s parents spilt up. I’d like to explore that more, because so many kids today come from broken homes.”

Wiseman and Black have two other huge youth projects on their hands. They have written the Song for Peace that will be performed in thousands of schools on September 21 — a date apparently now known as World Peace Day. The performances will be simultaneous, at least in theory. “I don’t know who will give the downbeat,” Wiseman giggles.

Black says that his lyric, No Wars Will Stop Us Singing, was inspired by watching news bulletins that showed fighting going on in streets where children were playing. Wiseman set his words to a broad, anthemic tune, and the song (first published in Youth Music’s superb Singbook collection) is already a hit in classrooms. I know — I have heard children singing it on a bus.

Their other project is an attempt to do a 21st-century equivalent of Britten’s Young Person’s Guide to the Orchestra. “The orchestra is such a wonderful beast,” Wiseman says. “We wanted to make it more immediate for kids.”

Their work, called Different Voices, will be set in a park where children realise they have to work “as one” if they want to save their playground. It’s a metaphor, of course. “We tie the thing together with a song that Hayley Westenra will sing,” Wiseman says. “Then I use melodic strands from it to introduce the different ‘voices’ in the orchestra. It will be premiered by the Royal Philharmonic next Easter, then turned into an animated TV film.”

It sounds enthralling. But can they really hope to equal Britten’s classic 1945 score? “Well, this may sound like heresy,” Black says, “but the Young Person’s Guide does sound a bit dated now. This is another way of putting it for a new generation.”

Feather Boy runs at the Brighton Dome and Lyric Hammersmith next week and the National Theatre (020- 7452 3000) on July 15. Full details: www.shellconnections.org