An “administrative error” saw a former Swaffham school named the joint third worst in the country in the Department for Education’s league table for GCSE results.
According to government figures, only 19 per cent of Swaffham Hamond’s High School students gained five or more A* to C GCSEs, including English and maths, in 2012.
But in fact 41 per cent of students received at least five GCSEs above grade C, including English and maths, and 73 per cent got five or more A* to C grades overall.
Hamond’s High closed last November and re-opened as the Nicholas Hamond Academy.
Assistant principal Martin Budgett said: “The 19 per cent figure is the result of an administration error and relates to a school which has now closed.
“No student was adversely affected and all progressed successfully to the next stage of their education, training or employment.”
Mr Budgett said the academy has “high expectations” for this summer’s exams.
He added: “Students and staff have a strong determination to be the best they can be and, with the wider community, achieve outstanding outcomes in the near future.”