As head of one of the country’s most prestigious public schools, Anthony Seldon has often claimed that schools have turned into “exam factories.”

Under his headship, the £33,000-a-year Wellington College has taken a more touchy-feely approach to education, not least with the introduction of “happiness lessons”.

But an exam results crisis at Wellington Academy, the state school it sponsors, has forced even Dr Seldon onto the “grade C or bust” bandwagon.

The college has launched an academic drive to raise standards at its state protégé, including bussing in English GCSE C/D borderline students for extra lessons on Saturday mornings.

Between 20 and 40 Year 11 pupils take the hour-long trip from the Wiltshire academy to Crowthorne, Berkshire to be tutored by Wellington College staff.

In addition to the C/D borderline classes, the college is hosting a series of three academic days, where all 150 members of year 11 at the academy travel to the college to work alongside privately-educated pupils on English, maths and science.

Teachers at the state school have also all been assigned a teaching “buddy” from the private school, who they can call upon for advice and share ideas and resources.

The aim of the drive is to drag the proportion of students gaining five A* to C grades with English and maths at GCSE up from 37 per cent to the 50 per cent government floor target.

In the summer, the head of the academy, Andy Schofield, was squeezed out over the poor results, and Anthony Seldon himself stepped in as executive principal.

The college has since appointed Mike Milner, Wellington College’s former director of studies, as permanent principal.

Cressida Henderson, assistant head at Wellington College, said the academic drive came as her school was easing its ambitions to sponsor a wider chain of academies until they “got their house in order” with standards at its first academy.

The private school will, however, open a brand new primary academy near to Wellington Academy in September and have not ruled out opening more if they are successful.

Ms Henderson, who oversees links with academies, admitted that the college had made mistakes when launching the state academy - largely by not interfering enough.

“We didn’t want to be seen as too overbearing or interfering, we didn’t want to be accused of arrogance, or of not knowing what it is really like to run a state school,” she said.

Ms Henderson pointed out that appointing a former member of staff from the college as principal had now brought the schools closer together.

“We left the academy to itself too much and the academy didn’t want our interference, but that has changed,” she added.

The new range of academic link-ups was designed to raise aspirations of academy pupils, she said.

“Some are not as ambitious about their education as they could be,” Ms Henderson added.