Two of Norfolk's highest-flying academies have seen their GCSE results crash to earth in a year which saw the government toughen up league table rules.

Ormiston Victory Academy, in Costessey, saw the proportion of pupils gaining the government's gold standard of five GCSEs at A*-C, including English and maths, fall by 30pc points - from 73pc last year, to 43pc this year - and Ormiston Venture Academy, in Gorleston, saw its results fall from 58pc to 43pc.

The academies are two of only three Norfolk high schools given Ofsted's 'outstanding' rating since it became harder to receive the top grade, and have been held up as examples by ministers and the inspectorate.

Analysis: Why have GCSE results at Ormiston Victory and Ormiston Venture fallen so far?

In a statement, Ormiston Academies Trust said it was 'not appropriate simply to compare this year's figures with previous years' figures', because of the changes introduced to league table criteria this year.

These included stripping out a number of non-GCSE qualifications which were previously counted as equivalent to one or more GCSEs, and only counting a pupil's first attempt at an exam.

These reforms contributed to a nation-wide 4.7pc point fall in pupils in state-funded schools gaining the gold standard. The Norfolk average fell less sharply, from 54.4p to 52pc.

Nicole McCartney, national director of performance and partnerships for Ormiston Academies Trust - and executive principal at Venture - said the schools 'proactively re-focused their curriculum' last year so that, after concentrating on English and maths, more students now take a greater range of academic GCSEs.

She said this was a 'turning point that will be for the benefit of children in the longer term'.

Naomi Palmer, principal at Victory, said: 'For the fourth year in a row since becoming an Ormiston academy, the proportion of students gaining a C in both English and maths GCSEs (57pc) was above the national figure, and many more of our students are now taking GCSEs in other academic subjects.

'Further, the gap between vulnerable and non-vulnerable students is a quarter of that of the national average. With such a talented group of staff and young people, we will be going from strength to strength in the future.'

Simon Gilbert-Barnham, principal of Venture, said progress of students in maths had met national standards, and 'far surpassed' them in English.

Outstanding schools are exempt from regular inspections, but Ofsted rules state inspections can be triggered if the chief inspector or secretary of state 'has concerns about a school's performance'.

It is not know whether this summer's fall in results at the two academies could lead to re-inspections, and an Ofsted spokesman said it 'would not comment on an inspection in advance'.

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