Steve Fickinger was sitting in his office on 42nd Street when he got a call from someone at the Disney Channel

“We’ve got a new film coming up,” said the colleague. “We thought you might like to do a stage version of it.”

“Send it over,” said Steve Fickinger.

Fickinger works for Disney’s theatrical group. The Disney Channel churns out low-budget kids’ movies, and at the Disney Theatrical Group, they develop some of those into stage musicals that can be licensed to schools.

When Fickinger got the film, he liked what he saw. “We’d no reason to believe that it was anything other than just another film,” he remembers, now. “But it was immediately clear that it was appealing.” He put a team to work, getting the adaptation ready.

Then, in January 2006, the film premiered on the Disney Channel. It was, to adult eyes, remarkably innocuous: it was called ‘High School Musical’, and told an unoriginal tale of a boy and girl from opposite sides of the classroom falling in love while working on their high school musical.

To younger eyes, though, it contained some kind of magic. Each time it was repeated by the Disney Channel during its first week, the audience grew (the opposite is normally the case with new films). Disney recorded a soundtrack in five days, and it became an immediate download hit, and later the top selling album in the US in 2006. ‘High School Musical’ has now been seen by 290 million people.

That summer, the stage adaptation went on sale to schools, and became the fastest-selling title in the Disney Theatrical Group’s stable. There have now been 3,400 separate stage productions of ‘HSM’ (as it’s known). Some three thousand of these have been by high schools, with 500 or so school productions staged in the UK, and 60, so far, in Ireland. A school can buy the rights to the show, with the script and score, for as little as €400. (Optional extras include a backing-track CD, for schools without a band or orchestra.)

The maths on this are quite extraordinary. Take an average school cast of 20 (though the cast is limitless, thanks to a flexible chorus), and a typical high school audience (in the US) of 500 a night, for 3 nights. That means 60,000 or so kids have performed in ‘High School Musical’. Maybe 7.5 million children (and their chaperones) have seen it live at their local school.

This phenomenon has subverted the normal marketing approach to musicals. More typically, the performance rights for schools and amateur groups are withheld till after the professional tours have come to the end of their life. But the ‘HSM’ schools effect created a ‘positive feedback loop’. Kids who saw it, or starred in it, at school, became even keener to see it on stage in a professional production.

‘High School Musical’ opened at the Gaiety last week. This production, produced by Adam Spiegel, comes from the UK; when its tour finishes, in August, it will have been on the road for nearly two years. Then Spiegel goes into production with the stage version of ‘High School Musical 2’. (The tv premiere was watched by a record 18.6 million people, and 300 million have now seen it. There’s also a third instalment, released in cinemas last October.)

“I’ve never seen numbers like this before,” says Spiegel of ticket sales for the stage show. And it’s not simply that it is commercially successful. “There’s palpably something different going on. Nothing quite prepares you for a night at the theatre at ‘High School Musical’.

“It’s like an enormous children’s party. Most of the audience are from five to fifteen, with their parents, but there’s a little bit of a hen-party element to it as well. There’s a bizarre cross-section in the audience.”

Neither of these advocates claims that ‘HSM’ is great art, though Steve Fickinger is adamant that it tells a story that youngsters want, and need, to hear: “that you can dare to break the mould that society has designed for you”.

Some of the London critics were sceptical. The Independent wrote that it “makes ‘Grease’ look like Sarah Kane’s ‘Blasted’”. In the Guardian, Lyn Gardner wrote that it was “like spending an eternity being jumped all over by an enthusiastic but incontinent puppy whose persistent yap says: ‘Love me! Love me!’” and that it was “not about art, but about artfully parting you from your cash”. But the Times thought it “a terrific success in its way”, and the Telegraph’s Charles Spencer found there was “something genuinely uplifting about so many children having so much fun”.

Being surrounded by a thousand tweenagers doing badly synchronised dance moves is not generally my idea of a good night at the theatre. But HSM has been more than a success: it has been a phenomenon, and that phenomenon has been fuelled, in part, by giving children the chance to star in their own school productions. That has to be good for the theatre.

(Incidentally, would-be musical writers are invited to a new initiative, the Dublin Musical Theatre Workshop, being run by composer Bernard Reilly and lyricist Shawn Sturnick, launching on March 30. Email dublinmusicals@gmail.com for more details.)

Written for my Saturday theatre column in the Irish Independent. See also the subsequent review.