It is one of the most high profile partnerships between a state and private school in the country, but Wellington Academy - sponsored by the elite Wellington College - has announced the departure of its headteacher after a dramatic fall in GCSE results.

Andy Schofield, who was founding principal of the academy, has stepped down from his position after four years due to what the College called a “decline” in academic progress.

The news will come as a significant blow not just to Wellington College and its master Anthony Seldon, but also to education secretary Michael Gove and even prime minister David Cameron, who have both lavished praise on the private school for sponsoring the academy.

In a speech in 2011, Mr Gove used Wellington’s example to put pressure on other private schools to sponsor academies, asking the question: “If you’re so good, why is Anthony Seldon proving that he is better at transforming state education than you are?”

The Wellington partnership has since been used as a shining example of why top fee-paying institutions should sponsor struggling state schools. Before this year’s slump, the school had gone from being the worst-performing in Wiltshire to the best in the county for value-added results at GCSE. 

For years politicians have been urging private schools to become more heavily involved in the state sector, with former schools secretary Lord Andrew Adonis once telling headmasters from the country’s elite independents, “We want your educational DNA”.

But results at Wellington Academy fell from 47 per cent of students achieving five A* to C grades including English and maths last year to just 37 per cent this summer, despite being partnered with the £33,000-a-year College.

It is understood that the academy’s governors decided that the fall meant that a change in leadership was needed.

Dr Seldon has been announced as the executive head of the academy, with Mike Milner seconded from the College as the school’s acting principal. 

In a statement released this afternoon, Mr Seldon said he was proud of what the school had achieved so far, but added that more needed to be done.

“We’ve taken action because these results are unacceptable,” he said. “We profoundly believe that all the children in the Wellington family of schools deserve to be set rigorous and ambitious targets and to have a culture of aspiration aiming at the very highest grades. That is what we want for every academy pupil.”