In 1989 just 2 per cent of pupils at Cornwallis technology college got five Cs or better. Last year the figure jumped to 68 per cent and this year it was 67 per cent.
Mike Wood, headteacher of the Maidstone school, said the improvements would not have been possible without specialist status - and the additional pound;1 million investment which it brought.
"When I arrived in the mid-1980s I was told you couldn't expect much from the pupils at a school which was in reality a secondary modern," he said.
"Specialist status helped create an ethos of research, aspiration and achievement."
The 1,600-pupil school now has results that make it the envy of some of the county's selective schools.
Last year the proportion of pupils getting five or more GCSEs at grade C or better was 14 percentage points higher than the county average.
Mr Wood puts much of the progress down to the school's ability to network and make links with other schools. He also praises the support it has received from the Specialist Schools Trust.
"But, of course, the money has helped," he said. "It has been an extremely valuable resource and I can't get away from the fact that well over pound;1m has been spent on the school, a lot of it on technology."
The school was the first in the country to have a computer sytem with wireless connections installed.
It also pioneered the widespread use of laptops and can now boast almost one computer per two pupils. The school has access to its intranet and the internet from every classroom.
Mr Wood said teachers could deliver the curriculum more effectively, while the information technology skills pupils developed had improved their performance in all subjects.
"Specialist status demanded an examination of our curriculum, placed us under the scrutiny of outside consultants, demanded that we engage with sponsors and placed us in a national network of like-minded aspirational schools," he said.
"Becoming a specialist school was one step on a journey of development but has given the staff the confidence to experiment and to take risks in the interests of improving opportunities and outcomes for our pupils."
He said the school was proud of its reputation for bringing the best out of its pupils. The school won an award last year from the Specialist Schools Trust for "value added".