The Peterborough School saw 98 per cent of pupils gain five or more passes.
Including English and maths, that figure was 89 per cent.
Fifty-six per cent of the old style grades were at A or A* (84 per cent at A*-B) and 10 per cent of English and maths grades received a top mark of nine under the new system, more than three times the reported national figure.
Thirty-nine per cent amassed at least eight GCSEs at A or A*/Grade 9-7. Among these, Chloe Hayes achieved an almost perfect combination of grade 9s and A*s in her 11.5 subjects.
Other top performers included Diya Banerjee, Olivia Barnes, Hannah Bassett, Georgina Parker and Joyce Ye, who were all in the top categories of A/A* or 9-7.
Headmaster Adrian Meadows said: “Our students have performed exceptionally well with the more challenging GCSEs; the number gaining benchmark grades is extremely high and I congratulate them all.
“We have not seen the predicted volatility in grades but rather a swelling in the number gaining the top grades and I am delighted that so many students will be carrying very strong results into the sixth form.”