An academy described by Tony Blair as the future of British education has been told it must improve or face closure.
The Business academy in Bexley, south-east London, was judged inadequate by inspectors who found large numbers of unsatisfactory lessons contributing to poor behaviour among pupils.
School leaders had failed to act quickly enough to improve the one in six secondary lessons which failed to make the grade, Ofsted said.
Bexley - one of a handful of state schools to take pupils aged 4 to 19 - was given notice to improve. This means it faces reinspection within 12 months. If it fails to show improvement, it will be placed in special measures with the threat of closure within a year.
The academy has found it hard to recruit and retain high-quality teachers and has faced considerable challenges as it has expanded the age range of the pupils it teaches, inspectors said.
Ofsted's verdict is a blow for the academies programme and will be seized upon by Labour backbenchers who are opposing further reforms in the Government's schools white paper. It is the second academy in a year to be found to offer an inadequate education, following Ofsted's criticism of the Unity academy, Middlesbrough.
Inspectors found that the pound;36 million London school, designed by Norman Foster, failed to provide value for money. They said that it lacked strategic leadership in the sixth-form and had courses which failed to meet the needs of students.
In 2005, only two out of 20 students taking the international baccalaureate got a full diploma and four out of six students who took an advanced vocational certificate of education in business failed to pass any units.
Despite these criticisms, Ofsted found pupils were positive about the school. It said poor behaviour was generally caused by ineffective teaching. Primary teaching was judged satisfactory.
Sam Price, chief executive of the academy, said: "Although Ofsted recognised our weaknesses in comparison to the national picture they also recognised the enormity of the job in hand and the progress we are making towards creating an excellent school in difficult circumstances.
"The academy still has a long way to go and that constructive criticism, such as offered by Ofsted, is a welcome part of the improvement process."
A Department for Education and Skills spokesman said: "You cannot judge the whole academy programme by one example. Bexley has made a major improvement on the results of its predecessor school."