Rule changes affected benchmark GCSE performance at some of the schools in Brighton and Hove as thousands of students celebrated excellent results.
Among the state schools the Brighton Aldridge Community Academy (BACA) was the only one to record an improvement in the benchmark of five good GCSEs.
Five good GCSEs are regarded as five graded A* to C including English and maths.
The Brighton and Hove average dropped to 54 per cent from 62.6 per cent a year ago.
Dorothy Stringer recorded the best results in the state sector as 65 per cent of pupils recorded five good GCSEs, compared with 72 per cent last year. The school said that 27 per cent of the grades were A* or A.
Head teacher Richard Bradford said: “I am proud of the students who worked hard and challenged themselves do their best.
“Many are celebrating excellent personal academic achievements at all levels.
“I would also like to thank staff and parents who have worked incredibly hard.”
At Hove Park the benchmark figure was 62 per cent, down on the 65 per cent recorded last year.
Head teacher Derek Trimmer said: “Students have improved their performance across the board at Hove Park School.
“Student progress has made huge leaps forward, with pupil premium and gifted and talented students the most successful.
“In English and maths the number of students making three levels of progress during their time at secondary school – probably the fairest way to measure a school’s effectiveness – has risen to 12 percentage points above the national average in English and just above the national average in maths.
“The most disadvantaged students, who are eligible for extra funding through the Pupil Premium, have performed particularly well, with a gap of only 14 per cent between FSM (free school meals) and non-FSM, half the national average.
“In most schools there is a clear gap between FSM and non-FSM students. At Hove Park we have managed to reduce that gap.
At Cardinal Newman 61 per cent of pupils achieved five good GCSEs, compared with 73 per cent last year.
At Blatchington Mill the benchmark figure was 59 per cent, compared with 72 per cent last year.
Head teacher Janet Felkin said: “The school results are very different to usual due to changes in the way that schools are measured.”
She said: “The turbulence caused by sweeping changes to government league tables affected the headline figures for the school but crucially made no difference to the students or their grades.
“Our staff and students have worked extremely hard to achieve these wonderful grades.
“These students have achieved more top grades than ever before.
“We knew the changes to league tables this year would not allow us to compare favourably to last year but, considering student success individually, demonstrates a very positive picture indeed.
“As a result, school league table figures do not count all qualifications, and are therefore not directly comparable to prior years.”
The Portslade Aldridge Community Academy (PACA) reported that 53 per cent pupils achieved five good GCSEs, down from 60 per cent.
And at Longhill High School the headline result dropped just one percentage point to 49 per cent from 50 per cent last year.
Head teacher Haydn Stride is confident that the attainment gap between poorer and better off pupils, measured by eligibility for free school meals, will show a closing of the gap. And progress on narrowing the attainment will compare well nationally too.
At Patcham High 49 per cent of pupils managed five good GCSEs, down from 55 per cent last year.
At the Brighton Aldridge Community Academy (BACA) 48 per cent of pupils achieved five good GCSEs, up from 46 per cent last year.
At Varndean School the figure this year was also 48 per cent. Head teacher William Deighan said: “We will analyse the variations that have happened nationally to discover the reasons for this.”
At Brighton College pupils “enjoyed another impressive year, with the pass rate at 100 per cent and 99.2 per cent of grades A* to B”.
The school said: “Once again, the most common grade awarded to Brighton’s GCSE candidates this year was A*, with 88 per cent of grades at A* or A.
“These are comfortably the best results in Sussex and are likely to place Brighton among the top five co-educational schools in England for the eighth year in succession.”
Brighton and Hove High School said that its girls were “celebrating outstanding success at GCSE with 58 per cent of all results at A* or A grades and a pass rate of 97 per cent A* to C”.
Head teacher Jennifer Smith said: “The governors and I are delighted with our girls’ success.
“They have worked tremendously hard and it is well-deserved.
“I am really pleased by the girls’ results – over a third of them achieved nine or more A* or A grades in challenging subjects. Congratulations to all the girls and staff on a superb performance.”