Northampton School for Boys has topped the town's league tables thanks to its score in the Progress 8 benchmark.
The Government's Progress 8 score rates students' performance from the end of Year 6 up until their GCSE results in Year 11.
NSB's score of +0.65 means that on average its students score is almost two-thirds of a grade higher per GCSE entry than students of similar ability across England and +0.90 of a grade above the 2018 national average for boys (-0.25).
This score puts them in the 'Well Above Average' bracket and significantly inside the top ten per cent of all schools nationally.
Headmaster Richard Bernard said: "These GCSE figures are indicative of outstanding teaching and an excellent student work ethic but most importantly give our students a huge advantage as they enter the next stage of their career pathway, be that post 16 education or employment.
"I am also delighted that as well as gaining an exceptional progress score we were top of the county rankings for the percentage of students achieving Grade 5 and above in English and Maths (74%) which are again crucial core skills for future success in life.'
Northampton School for Girls also performed above the national average with a progress score of +0.33.
The full table of Northampton results is shown here and are published by the DfE in October to help parents and carers who are deciding upon secondary school choices for children who are in Year 6.