But one of the Government’s biggest academy sponsors, the charity Ark (Absolute Return for Kids), has hit problems with its much-vaunted plans to open seven new schools in London by the end of 2008.

Lucy Heller, Ark’s general manager for education, said it had delayed next month’s opening of a 900-student academy, for pupils aged four to 18 in Westminster. It will now open in September next year as, she said, there was not enough time to enrol students and the council no longer urgently needed the primary places.

Another of the seven Ark academies might not open as planned by the end of 2008, and one of its academies may now be outside London, she said.

Last year, Ark withdrew from its flagship academy project in Islington after protests from parents and teachers against “fatcats” running schools.

Ms Heller said the charity withdrew simply because it was committed to an academy that ran through from nursery to sixth form, but its plan to include a primary on the same site had fallen through.

Ark was set up by “Arki” Busson, 42, the French multi-millionaire financier and father of model Elle Macpherson’s two children, who is also famous for organising Britain’s richest celebrity fundraising auctions.

The charity says on its website that it intends to have 4,500 students enrolled in seven academies by the end of 2008. Eventually they will hold at least 7,000 students.

But only one of these will be ready to open next month. Another four have reached “feasibility” stage - an approval in principle allowing detailed planning before the Department for Education and Skills signs off their funding. The delayed Westminster project is among these four.

Westminster council said it had reviewed school admissions in May and decided that it would be “more beneficial” to delay the academy’s opening by a year.

The only Ark school which is on track to open next month is a 1,200-pupil 11-18 academy in Hammersmith, run in partnership with the diocese of London, to replace the failing Burlington Danes Church of England 11-16 school.

Spokey Wheeler, head of Burlington Danes academy, said he would look forward to working with the other schools when they opened, but for now “I think we’ve got our hands full”.

As an academy specialising in arts and maths, his school will work with the local Lyric Theatre and the BBC, and plans to open its own 300-seat theatre. By creating four distinct small “schools” in the 1,200-pupil academy, he hopes to emulate “the best of transatlantic practice” as exemplified by US charter schools.

To this end, Ark has flown in Jay Altman - a teacher who pioneered charter schools in New Orleans in the early 1990s - as education director.

The delayed Westminster academy, with the working title “Westminster 4”, is one of two schools the charity plans to open in 2007; the other is an academy in Southwark to replace Walworth school, initially in its existing buildings.

The charity also plans to open a new 11-18 academy in former primary school buildings in Brixton in late 2008, following a campaign by parents for new secondaries in Lambeth.

Ark also plans to open a 3-18 academy in the Elephant and Castle area to replace Geoffrey Chaucer college and Joseph Lancaster primary school.