Private schools have reported an increase in the number of A* grades awarded to their pupils at GCSE and IGCSE.
The Independent Schools Council, which represents nearly 1,300 schools, said the number of A*s awarded in the qualifications had risen 1.6 percentage points to 34.5 per cent of all grades in 2016.
The figures are not directly comparable with national figures for GCSE as they include IGCSE grades.
However, national figures for all schools at GCSE alone, published last month, show that just 6.5 per cent of grades were awarded at the top grade, a fall of 0.1 percentage points this year.
The ISC said the proportion of its candidates achieving five or more GCSE or IGCSE A*-C grades, including English and maths, increased 0.7 percentage points to 90.8 per cent in the 552 schools surveyed this year.
The EBacc effect
Nationally, the proportion of GCSE entries receiving A*-C grades fell by 2.1 per percentage points on last year to 66.9 per cent.
This was the biggest ever national drop since the exams were introduced more than 25 years ago. Headteachers put this down to schools entering weaker pupils for more "academic" subjects in order to achieve higher scores on the English Baccalaureate measure.
IGCSEs are not regulated by Ofqual and were removed from league tables in 2014. This led to many schools, mainly those in the independent sector, receiving a score of zero in the measure for pupils’ achieving five A*-C GCSEs, including English and maths.
Despite protests from schools, the government has refused to budge, saying that including results for IGCSE and other alternative qualifications in national results would "undermine the rigour of our qualifications".
A note on the ISC’s press release relating to today’s figures said: "Results from ISC schools include IGCSE as well as GCSE. ISC continues to believe there are no grounds for the separation of performance of the IGCSE from the GCSE."
Today’s figures follow research earlier this year from the Centre for Evaluation and Monitoring (CEM) at Durham University, which suggested that attending an independent school in England could add the equivalent of two additional years of schooling by the age of 16.
The results also come after the TES reported that private schools were increasingly turning their backs on GCSEs because they were "uninspiring".
'Formative stepping stone'
Barnaby Lenon, chair of the ISC, said: "To see an increase in independent school grades across the board is excellent news and testament to all those working hard in our schools – and of course to the young men and women who sat the exams having built towards them for a number of years.
"Set against a decrease in numbers nationally and in an environment where there are efforts to halt grade inflation, this is particularly impressive."
Julie Robinson, ISC general secretary, said: "Once again, the value of an independent education can be seen through the achievements of the students in our schools.
"GCSEs might not be the most popular of exams – and some commentators have questioned the validity of public examinations at this point in a student’s education.
"However, our schools put much emphasis on the core subjects of English, maths, sciences and languages, much-prized by universities and employers, so these exams continue to be a formative stepping stone for our pupils."