Andrew Lloyd Webber says his new musical will challenge politicians to improve school music lesson funding.
School of Rock, based on the 2002 film, is about a group of schoolchildren who turn their lives around by entering a Battle of the Bands contest.
The young cast - aged between nine and 12 - all play their own instruments.
"At this time when there are cuts to music in schools, these are the kids that prove music is vital," Lord Lloyd-Webber told the BBC.
He said music "is a force for the good and empowers young people".
'Alienated from politics'
The composer, whose own foundation funds arts education programmes in the UK, said the government should rethink its "counter-productive" cuts.
"At a time when people are feeling alienated from politics, the arts cut right through that," he said.
Downton Abbey creator Julian Fellowes, who wrote the musical's book, picked up on the theme.
"One of the main purposes of the education years is to help children find out who they are and what they want to do, and the arts are one of the greatest means of allowing people to discover their identity," he said.
"It really is mad for the country to cut back on that and throw out a whole load of people from school who really haven't found out what they want to do."
Lord Lloyd-Webber and Lord Fellowes were speaking as they unveiled the cast for the West End transfer of School of Rock, which opened to enthusiastic reviews on Broadway last year, earning four Tony Award nominations.
The show, based on the Jack Black film, features three rotating casts of child actors, selected after a nationwide search earlier this year.
They range from experienced actors, drawn from the casts of Matilda and The Lion King, to complete newcomers.
Among them is Amelia Poggenpoel, from Formby, who made headlines last year when her singing reduced Shia LaBeouf to tears.
The 10-year-old approached LaBeouf at his #TouchMySoul exhibition in Liverpool and performed Who's Lovin' You by the Jackson Five. When she finished, the actor stood up and hugged her, sobbing: "You touched my soul."
She will play Shonelle in the musical, her first West End role after several appearances in Liverpool.
Amelia told the BBC she was living in a "School of Rock house" with other cast members, where tutors run lessons before and after rehearsals. The set up is "much better" than regular school, she added.
Other cast members include Isabelle Methven and Eva Trodd, both 11, who previously played Little Cosette in the West End production of Les Miserables, and Natasha Raphael, 10, who toured the UK in the role of Annie last year.
Toby Lee, an 11-year-old from Priors Marston who runs a successful YouTube channel showcasing his guitar skills, is one of three youngsters filling the role of Zack.
'Depth of talent'
The show revolves around failed rock star Dewey Finn who, in need of cash to pay his rent, fakes his credentials as a substitute teacher.
But what starts out as an excuse to get paid for slacking off turns into a life-affirming experience, as he prepares his pupils for a local battle of the bands.
"The reason I loved this story is every character in this story is somehow changed for the better through music," said Lord Lloyd-Webber, who first revealed he had bought the rights in 2013.
For the first time since Jesus Christ Superstar in 1971, he chose to premiere his new show in the US, principally because it has more relaxed child labour laws - meaning the production could have one permanent cast.
He previously expressed misgivings about bringing the show to London, saying he doubted whether he could find 39 children capable of pulling off the live musical elements of the show.
Instead, he said, "we could have found five bands to play".
"The depth of musical talent that we auditioned is something that I have to admit I didn't think we would find. I kind of feared they'd all be into their computers, but this proves that they aren't."
The role of Dewey Finn will be played in London by David Fynn, currently starring in US sitcom Undateable.
He said working with three rotating casts of children helped give the show spontaneity.
"It keeps me on my toes and, as a result, it helps them stay engaged."
The show begins previews at the New London Theatre on 24 October before opening night on 14 November.