Endeavour High School, on Beverley Road, Hull, joins David Lister School which is also in special measures following a recent visit by a team of Ofsted inspectors.

A report has not yet been published but a source says the local education authority consider it a "harsh judgment."

Last year only 18.5 per cent of pupils achieved the Government benchmark of five A* to C grades, however three other schools in the city, Kingswood, Pickering High and David Lister – where only 10 per cent made the grade – fared worse.

The source said the decision did not make sense as the report praised its leadership and did not find any unsatisfactory teaching. "If they'd waited another month (for the results) they'd either have the school bang to rights or possibly look a bit foolish. This year Endeavour's target is 25 and the school is very confident that can be exceeded and even hit 30."

Endeavour – nearly 20 per cent of whose pupils do not speak English as a first language – was made the subject of an improvement notice last March.

Inspectors last visited in November and judged it as making satisfactory progress, praising it for developing an "innovative range of strategies" which had bought the school "enormous benefits."

The report said there had been a big drop in exclusions and staff absences. "Students say that behaviour is good, that the school is a respectful, safe and welcoming community and that they are proud of the improvements that have been made."

However, they warned that satisfactory teaching alone would not bring about a big enough rise in standards. Hull Council could not comment until the report is published.