Eastbourne College achieved a grade nine, eight or seven - which is the equivalent to an A* to A - in 60 per cent of their GCSE results.
The school had 118 students in total sit their GCSEs this year.
Thirty-five per cent of results achieved were a nine to eight grade mark (A*).
Seventy pupils achieved a grade nine to seven in at least half (five) of their subjects.
Headmaster Tom Lawson said, “I am delighted by the performance of our pupils at GCSE this year, with our best ever results in the reformed exams. The large number of outstanding grades, as well as strong value added for pupils across the ability range, is a testament to the hard work of teachers and pupils.”
The school excelled in the sciences and saw 80 per cent of grades awarded a nine to seven in biology, chemistry and physics.
In maths, almost 60 per cent of the grades were awarded a nine to seven.
Art, Greek, history, Latin, modern foreign languages (French, German, Spanish), music and physical Eeucation all performed strongly with the most common grade in each subject being a nine, eight or seven.
The school saw a rise in elite performers with 35 pupils achieving eight or more nine to seven grades.
Seventeen pupils achieved eight or more nine to eight grades (A*).
Notable top performers were Tianlu Wang who earned 11 nine grades, one eight grade and an A* in Chinese.
Tom Meek was awarded nine nine grades and two eight grades.
Rebekah Agunede was awarded eight nine grades and two eight grades and Oliver van Noort achieved seven nine grades and four eight grades.
Other top performances came from Louis Loubser, Arnold Shum and Natasha Symes who all achieved seven or more GCSEs at grade nine, and Ben Scanlan was awarded ten nine to eight grades and two seven grades.
Twenty-four year 10 pupils took their maths GCSE a year early, with 21 achieving a nine or eight grade.