The Bishop of Norwich has told parents of his concern after Ofsted inspectors who were ordered to re-visit Norfolk's first academy school downgraded the initial 'good' verdict to 'requires improvement'.

The original report, which was not made public but was leaked to this paper, followed an inspection in June, and said the Open Academy in Norwich was 'good' across the board.

However, senior Ofsted officials Paul Brooker and Sean Harford returned to the school in July and the final report, published on the school's website this week, says it 'requires improvement' overall, as well as in the categories for achievement of pupils and quality of teaching.

Since the second inspection, the multi-million pound academy, in Heartsease, Norwich, saw the percentage of students gaining five A*-C GCSEs, including English and maths, fall to 35pc from 40pc last year – 5pc points below government target.

In a letter to parents, the Rt Rev Graham James, who is one of the school's sponsors, said: 'In an almost unprecedented situation, we received a phone call on publication day to say that we should not circulate the report yet.

'On July 2, we received a letter to say that we would 'receive an additional inspection visit'.'

The letter claims that during this week there were no classroom-based lessons, as pupils were taking part in activities such as work experience and activities week, but even so inspectors downgraded the judgment – despite only speaking to two students that day.

'We assure you that our resolve to be excellent has not diminished despite the impact this second inspection has had on staff morale and on some of the students.'

An Ofsted spokesman said: 'Ofsted carries out robust quality assurance procedures to ensure that inspection judgments are accurate, fair and supported by evidence. Sometimes this involves a further visit by Her Majesty's Inspectors to gain evidence to secure the judgments.'