Arabella Weir does not really mind whether her bum looks big perched on a child’s chair. She’d rather her local primary school continued to thrive.

And if that means using her famous catchphrase to draw attention to the school’s achievements, then so be it. Author and star of The Fast Show, Arabella (pictured, left) has been co-chair of the Parent Teacher Association at Ashmount Primary School in Highgate, north London, for six years.

But it was not until the school went into serious weaknesses in March 2003 that her support was truly needed - and tested. “The minute we went into serious weaknesses, parents started taking their children out of the school,” says Arabella, who has two youngsters at the primary.

“In my daughter’s class of 25, 11 upped and went almost immediately. It was a classic example of middle-class hysteria.”

“There’s this awful middle-class fantasy that poor children will somehow drag your brilliant kids down,” she adds. “They complain endlessly about how hopeless their local school is, without realising that they need to invest in it themselves if it is to improve. It enrages me that they don’t do anything and still complain that it’s not good enough.”

While some state schools struggle to get a handful of ordinary people on to the PTA, others have access to some extraordinarily well-connected parents.

Plenty of the rich and famous choose state schools for their children, and their support is incalculable. But most of them decide to keep their heads below the parapet, so you never know what they contribute. In Arabella’s case, her public profile has given a struggling school the help it needed to aid its recovery.

Ashmount is positioned between wealthy Highgate, a coveted conservation area, and a deprived housing estate. As such, it is a diverse school where 32 different languages are spoken. Other schools in the area are often labelled as either “worthy” or “undesirable” by well-heeled parents - something which all too often becomes a self-fulfilling prophecy.

In Ashmount’s case, the school came out of serious weaknesses after just a year and a half, thanks in part to Pana McGee, its dynamic new head. She has made parental commitment a priority to the recovery plan, and mums and dads are encouraged to come into the school to either help with the pupils’

reading programme or share their professional or personal experiences. But she also understands how useful celebrity endorsements can be.

“Arabella is newsworthy. She’s the currency and she can use her status and contacts to access a wider audience,” says Pana. “But it’s up to us to ensure that we deliver on our promises.”

Thanks to Arabella’s connections, Doctor Who star David Tennant attended a school fair this summer, helping to raise pound;7,000 in signed photographs and autographs. The school has also had Trevor Phillips, head of the Commission for Racial Equality, and Jon Snow, the Channel 4 newsreader, in to help raise pupil aspirations.

Ashmount is not the only school in north-west London - infamous heartland of the chattering classes - to harness the power of celebrity. Canonbury Primary in Islington has the dubious honour of not one but two education ministers as school parents: Andrew Adonis, the Schools Minister, and Boris Johnson, the Shadow Minister for Higher Education. At the school’s Auction of Promises this year, prizes included a guided tour round the House of Lords with Lord Adonis, which Mr Johnson won for pound;5,000. A private home concert from Chris Martin, the lead singer of Coldplay, went for the same amount - the band’s business manager, Paul Makin, is also a parent at Canonbury. In all, the school raised pound;43,000 from a single evening.

“We do have a lot of parents with connections here in Islington,” says Canonbury’s head, Jay Henderson. “We have some parents living in pound;5 million houses and others in cramped, two-bedroom council flats - it makes for a great mixed environment.

“We encourage all our parents to air their views and opinions as part of our Parent Link initiative and our PTA.”

Even schools without access to such influential celebrities can raise large sums of money. Last year, pound;73 million was raised nationwide by PTAs - an increase of 10 per cent on the previous year.

Arabella says: “I’m well aware that I have the time and contacts which can be helpful to a school, but anyone can make a difference. You don’t have to change the world, but you do have to do tiny gestures, like make a cake once a year and try to sell it”

The haves...

* Robbie Williams gave pound;50,000 to St Margaret Ward RC High School in Stoke-on-Trent, his old school. This rather put into the shade Mick Jagger’s donation of pound;10,000 to his alma mater, Dartford Grammar in Kent.

* Roman Abramovich, the Russian billionaire owner of Chelsea Football Club, donated pound;150,000 to Godolphin and Latymer in Hammersmith, west London, his daughter’s public school. This is a marked improvement on the previous year, when the school raised pound;122,000 from nearly 400 donors.

* Hampton Hill Junior School in Middlesex raised pound;25,000 with an auction of celebrity memorabilia from the Dalai Lama, Mick Jagger and Darcey Bussell on eBay. It has provided the school with an 18-terminal ICT suite and a sensory garden.

* Writer Nick Hornby took a leaf out of his own book, How To Be Good, by donating more than pound;2 million towards building a school for autistic children, including his own son.

...and the have-nots

Castlemilk High in Glasgow has no PTA and no intention of getting one in the foreseeable future. “If the parents told us they wanted a PTA, we’d organise one,” says Brian McAlinden, head. “We certainly don’t feel any less of a school without one.”

The south-east Glasgow school is based in one of the most deprived parts of Scotland. About 54 per cent of its pupils are entitled to free school meals and just 4 per cent go on to higher education.

Despite severe economic hardships, parents recently helped to raise more than pound;11,000 to send a group of pupils on a school trip to Uganda, and are well represented on the school board. “We tend not to have traditional parent-teacher fundraiser events but our parents are extremely supportive and involved in the school on an individual basis. Last week, 84 per cent attended our parents’ evening,” says Brian.

Castlemilk was one of 20 Scottish schools to be nominated by the Scottish Executive as a School of Ambition in 2005. As such, it will share Pounds 100,000 a year for three years with its bid partner St Margaret Mary’s Secondary and will help set new national standards in excellence.