Ofsted said that the pound;32 million City of London academy was "satisfactory" overall, but too many pupils were being held back because they struggled with basic reading and writing.
Last month, the Business academy in Bexley, Kent, was severely criticised by Ofsted and served with a "notice to improve", while the Unity City academy in Middlesbrough was placed in special measures last year. GCSE tables show half of academies are among the worst-performing 200 schools in England; however many were created from former failing schools.
Ofsted said literacy standards and test results at the City of London academy, sponsored by the Corporation of London, which opened in 2003, were too low but was "impressed" by its facilities, and pupils doing high numbers of extra-curricular activities.
Inspectors have failed another inner city school destined to be an academy.
The Geoffrey Chaucer technology college, also in Southwark, is now in special measures.