The building, which was heralded as an exemplar for school design at the 2004 Stirling Award, has been placed on the government's critical list for struggling schools.
While the report by the school inspection organisation condemns the teaching standard, and not the fabric of the school itself, it does leave doubt over the success of Foster's designs.
Ofsted found that the £31 million academy in Kent, hailed by Tony Blair as 'the future' for education - was not offering effective 'value for money'.
Poor teaching, bad behaviour in class and continued low exam results led inspectors to issue the school with an official 'notice to improve'.
The Ofsted inspectors said in their report: 'There are weaknesses which senior leaders have recognised but have not tackled speedily enough. The sixth-form provision is inadequate and success rates in Year 13 examinations in 2005 were poor.
'These weaknesses mean that value for money is not fully satisfactory.'
Since the academy was founded, some results among pupils who joined have shown improvements, and ministers hailed the school as evidence that their controversial £5 billion academy programme was working.
But the report says that the school only just avoided being placed in 'special measures', Ofsted's severest option.
It was given the lowest overall grade - a grade four - meaning that the academy was judged to be 'inadequate' overall.
The academy replaced the failing Thamesmead Comprehensive School, which was afflicted by vandalism, violence and truancy, with only one pupil in over 100 achieving five or more GCSEs at grade C or above in 2002.