Governors of the Greig city academy in the borough of Haringey, north London, have agreed to take the radical action after a critical report by inspectors they had hired privately.
David Triggs, principal of the Greensward College in Essex, will act as chief executive of the improvement team which will start at the academy after Easter and remain for at least four terms.
Greig, formerly the St David and St Katharine Church of England secondary school, opened in September as the first of the new academies.
The Haringey school was given more than pound;10 million by the Government and pound;2m by the Church of England and Greig Trust charity for rebuilding work.
An inspection arranged by governors and the Department for Education and Skills last month found some improvements, including mostly good or very good key stage 4 teaching. But they said that too much unsatisfactory teaching remained, particularly in lessons for 11 to 14-year-olds, and that pupil behaviour was often poor as a result.
The school's management was also criticised for ineffective planning, although the principal Graham Horsewood was praised for showing commitment to the school "at some personal cost".
The inspection report is the latest set back for the undersubscribed academy, which was forced to hand out leaflets outside local supermarkets last year in a bid to attract more pupils.
National Union of Teachers members at Greig are threatening industrial action next term over working hours. Teachers have been asked to work 1,400 hours a year instead of 1,265, and take two short breaks instead of a long lunch break.
Haringey NUT claims that the inspectors said the school's unusual hours were detrimental to pupils' education.
The failure of the flagship school will be an embarrassment to the Government.
But even opponents of city academies, including the Campaign for State Education, say that seven months is too short a time to transform a school in such demanding circumstances. More than half of Greig's pupils speak English as a second language and the majority receive free school meals.
Mr Triggs, whose own school Greensward is a specialist and beacon school, is assisting two other schools.
A DfES spokeswoman said: "Putting an improvement team into Greig in no way undermines our commitment to city academies - in fact, it reaffirms it."