Students at Warden Park Secondary Academy in Cuckfield achieved 'fantastic' GCSE results despite the more challenging examinations.
The proportion of students who achieved both English and maths at grade 9-4 is a 'headline measure' for schools nationally, the school said.
And the school's performance has improved to 79 per cent, from what was an already impressive 76 per cent last year.
Dom Kenrick, headteacher, said: “I am delighted that our Year 11 students have achieved such an outstanding set of results and it is a fitting reward for the determination to succeed academically that they have shown throughout their time at Warden Park.
"In an environment of increasingly challenging GCSE examinations our students have shown the growth mindset and grit to not only believe that they can be successful but to actually achieve it.
"I have been particularly impressed by the achievement of our students right across the ability range.
"For some students achieving grades 9 or 8 was the challenge whilst for others it was to achieve grades 4 or 3.
"Success today will look different for each and every student and the enormous pride I feel for my students’ achievements is not dependent on the grade achieved but on the work put in and the progress made that will allow them to move on to the next phase of their education.
"I would also like to express my thanks to my staff team for their dedication in ensuring that at Warden Park we achieve the best from all”.
A spokesman for the school added: "This exceptional set of GCSE results is a real testimony to the dedication and hard work of our students and our staff in achieving the Best from All.
"In English, 90 per cent of students achieved a grade 9-4 whilst in maths the figure was 82 per cent.
"We are equally delighted that the proportion of students achieving the very top grades of 9-7 was 36 per cent in English and 29 per cent in maths.
"Across all subjects a fantastic 30 per cent of the grades achieved by students were the very top 9-7 grades.
"In science, 74 per cent of all students achieved two science GCSEs at grades 9-4 whilst 80 per cent of those taking three science exams (biology, chemistry and physics) achieved a grade 9-4.
"Modern foreign languages had 79 per cent of students achieve a grade 9-4 whilst in humanities (geography or history) the figure was 81 per cent.
"Students’ achievements in the expressive arts (art and design, dance and music) was equally impressive with 88 per cent, 100 per cent and 78 per cent achieving grades 9-4 respectively.
"At Warden Park we offer a very wide range of subjects and in 22 of these subjects over 80 per cent of students achieved grades 9-4 which is a tremendous testimony to the strength of teaching across the curriculum and of students’ hard work here at Warden Park."