Figures released by the Independent Schools Information Service (ISIS) also showed more than nine out of 10 independent school entries were awarded grade C and above. Nationally, the numbers achieving A* to C grades rose to 55.8 per cent.
A record 50.3 per cent of independent school exam entries were graded A* or A, compared to 15.2 per cent nationally.
ISIS hailed the results as a "significant improvement" on last year's grades. Independent school candidates achieved an average of 59 GCSE points under a system where an A* is worth eight points, an A, seven, down to one point for a G grade.