Parent power: The comprehensive created by mums and dads

Drive past The Elmgreen School, in West Norwood, south London and all you will see is an unremarkable Victorian primary. Yet for some educational visionaries, this school is a blueprint for the future.

These are the people who want to see a thousand different schools blooming in the garden of education. They include David Cameron, the Tory party leader, and they are excited because the launch of The Elmgreen School this year shows that parents can start up their own school successfully within the maintained school system.

Elmgreen is a triumph for the small group of parents who battled for years to get a coeducational comprehensive for their part of suburban London. It also appears to lend weight to Cameron's energetic vision of families, charities, churches and philanthropists all being set free to found state-supported schools. But, in fact, the story of Elmgreen, while inspiring in its own right, shows just how unlikely it is that many parents, at least, will be responding to Cameron's call.

In Elmgreen's case, the area was chronically short of secondary school places. Half of all local 11-year-olds had to go to school out of their home borough of Lambeth, while the rest had to travel long distances within the borough, often to schools that were single-sex and faith-based. "Our driving force," says Sandy Nuttgens, a foundation governor and one of the leading campaigners, "was, 'Where on earth are our kids going to go to school?'"

The idea was first raised in 2003, and four years later, after a multitude of financial and bureaucratic setbacks, the school opened its doors in its interim home of a refurbished primary school. "It was incredibly moving on the first day to see the school actually, physically, there," says Isobel Bremner, chair of the Parents Promoters Foundation (PPF), the company formed out of the campaigning group that now acts as the educational foundation for the school. "All those children and staff! It was amazing. We had no models or anything to go on and we had to work incredibly hard to make it happen."

The school started last September with 180 Year 7s and will grow year by year until it is a fully fledged 11 to 18 secondary school in a £25m new building in Tulse Hill, designed by the fashionable architects Scott Brownrigg and David Adjaye Associates. One of the pioneer students is Nuttgens's daughter Mia, 12. "I really enjoy it," she says. "The teachers are nice."

"It's quite an optimistic school," agrees Damani McFarlane, 11. "Like, if you goof up, the teachers don't say that you've goofed intentionally. They try to help you with your work, and keep you focused."

The school has a greater number of parents on its governing body than other schools, and there are close links between home and school. The PPF puts on events such as a quiz night and a talk about teenage development, and parent-teacher communications are fostered through contact weeks, where parents can make appointments to suit their own schedules, in place of the traditional parents' evening.

But both sides stress that this not a parent-run school, and for head Asma Mansuri, a former deputy head in neighbouring Streatham, the most exciting aspect of her job is the chance to handpick her teachers and build a school from scratch. She has started with innovations such as no bells, and assemblies later in the day, not first thing.

"It's been a great gift, but it's also been a struggle because you are on your own at first, and you're dealing with everything, the design for the new site, the furniture, the uniform, people saying, 'Asma, what are we going to do about the catering?' You quickly become an expert on things like reheated food!"

The school was determined to open as a specialist school, and persuaded the Government to bend the rules – as a new school it couldn't furnish evidence of previous achievement – to allow it to set up as a school based on the humanities. It has a committed staff, a friendly atmosphere and a carefully thought out view of the culture it wants to foster – inclusive and respectful, with high standards and a commitment to all aspects of learning. Its reputation is growing rapidly and nearly 800 children applied for 180 places this year.

This will warm Cameron's heart. He wants to see "a new generation" of co-operative schools, and says that a Tory government would scrap existing rules that block the setting up of new schools when there are surplus places. "We know that if parents have a say in how their school in run, if they feel their views matter and their wishes count, the school is always better," he told an audience in Manchester last November. "What better way ... than to give them ownership of it? To make them not just stakeholders but shareholders."

Michael Gove, Shadow Schools Secretary, says this will be done by "radically building on existing academy legislation" to generate an environment in which many more good schools can be created – which the Conservatives propose to call new academies. "These will be free, non-selective, and within the maintained system," he says. "They will be smaller than comparable, existing schools, they will be set up and run by existing educational providers, charities, trusts, voluntary groups, philanthropists and co-operatives on behalf of parents and pupils, they will be not-for-profit organisations, and they will compete with surrounding local authority schools, helping to exert pressure for higher standards in the surrounding schools."

The Government, too, is keen to give parents a bigger involvement in setting up schools and legislated two years ago to encourage "parent promoters" to approach local authorities about building a new school in their area if they feel provision is inadequate.

But Elmgreen's battle-hardened campaigners doubt that what they did could be replicated easily. Nuttgens points out that the impetus for their school came from the local education authority, which suggested the plan and backed it when frustrated parents proved willing to run with the idea. The PPF was also lucky that a site was available for the new school. "And a lot of parents had to put an awful lot into it," he says. "Not a single one of us realised what was involved at the beginning. There was a core of about 13 and they were full-time parents, or people who could work flexibly, so they could give it their time. But most parents couldn't. I know people who have to have two jobs just to make ends meet, and who would never be able to find the time for this sort of campaign."

Moreover, the situation in which local parents found themselves really was awful, according to Kate Scrase, parent and PPF project manager consultant. "We collected a dossier of personal experiences, and they were just horrible. Children wetting beds because they were so worried about getting a school place and things like that. So there was massive motivation to get a campaign going."

But in Camden, north London, a similar campaign for a secondary school in the Holborn and St Pancras area, has roused equal passions but run into a brick wall of sky-high land values and an education authority that prefers to expand secondary schools elsewhere in the borough.

"There is a real hole in the policy," says Emma Jones, a coordinator of the Holborn and St Pancras Secondary School Campaign. "Things aren't focused on community and location. This area absolutely needs a school. The Government should be making provision for particular situations, rather than telling people to send their children miles away."

However, she, like the Elmgreen campaigners, emphasises that it is extremely difficult for parents to get a school off the ground. "It is extraordinarily hard work and very time consuming. Parents know about children, but they don't know about the education system. I can't see many wanting to do it."

Meanwhile, Steve Sinnott, general secretary of the National Union of Teachers, says that the Cameron approach would wreak chaos in the education system. "New schools will mean surplus places that will be massively costly and will draw funds away from existing schools," he says. "What you need is a system that properly funds and supports the places that are already in existence."

Also, he claims, research does not back the policy. "The only evidence that exists on these kinds of schools is on the charter schools in America, and that shows that they have no greater effectiveness than any other schools," he argues. "The structure of a school is not a prerequisite for excellence at all."

Emma Jones agrees that parent-promoted schools are unlikely to be automatically better than more traditional ones. "Just because people are parents, they are not necessarily angels," she says. "Parents can be just as selfish and snobbish as everyone else. In the end it comes down to what sort of society we want to live in. The best schools are those supported by their local communities. But education policy as it now stands is very divisive and splatters kids all over the place."

However, the Tories remain convinced by the appeal of parent power, and point to parent-backed schools in Spain and Sweden to make their case.

"We want to help parents who wish to set up a school and raise the standards of education for their children," says Gove. "That's a noble ambition that should be welcomed and supported, not crushed."