One in five of all GCSE entries from private schools scored the highest grade this summer - compared with one in 20 of entries as a whole, figures show.

Data published by the Independent Schools Council (ISC), which represents fee-paying schools, shows that 20.5 per cent of GCSE entries from private schools were awarded a grade 9, the new top grade.

That compares with 4.3 per cent of all UK GCSE entries, including students from both state and private schools, who achieved a grade 9.

Ed Elliott, headteacher of The Perse School, an independent school in Cambridge, said there was “no single ingredient for a grade 9” but that independent schools had “developed a winning formula that stretches all pupils and allows the brightest to achieve the best”.

Mr Elliott, who is also chairman of the Headmasters’ and Headmistresses’ Conference exams task group, added: “The formula includes highly qualified staff teaching in ways that maximise each child’s achievement, extracurricular and character education, a culture of high aspirations and positive peer groups in which it is cool to work hard and succeed.”

‘Quality of teaching and ambition’ in private schools

The ISC figures cover GCSE data collected from 549 UK independent schools on 37,913 candidates. They show that 62.6 per cent of entries scored at least an A grade, or a grade 7 under the new grading system.

Across the UK, 20.5 per cent of GCSE entries achieved this result.

The ISC also found that 87.7 per cent of candidates from independent schools gained at least one A*-A or 7-9 grade, while 73.7 per cent achieved at least one A*, or 8-9 grade.

Barnaby Lenon, ISC chairman, said: “The results demonstrate the quality of teaching and ambition in our schools and prove the vital contribution the sector makes to the British education system.”

Under the biggest shake-up of exams in a generation, GCSEs in England have been toughened up and a new 9-1 grading system has been introduced, replacing A*-G grades.

A new grade 7 is broadly equivalent to an A and a grade 4 broadly equivalent to a C.

The vast majority of entries in England this year were for the new-style GCSEs, while in the main, entries in Wales and Northern Ireland were graded A*-G as they have differing education systems.