Pupils from private and grammar schools disproportionately sit what is perceived to be the hardest computing A-level, fuelling fears that thousands of would-be computer scientists at comprehensive schools are not being given the chance to develop their skills.

Last summer, a quarter of entries from schools for the AQA exam board's computing A-level came from pupils at fee-paying or academically selective state secondaries, despite these pupils representing just 12% of England's school population.

According to the Department for Education, just 4.9% of pupils in England go to a grammar school, while 7% go to a fee-paying school. However, there were 1,183 entries from schools for the AQA exam, which is deemed to be the hardest of its kind by the British Computer Society (BCS). Of these entries, 13.4% were from grammars and 11.8% were from private schools.

A further 1,866 pupils took the exam from sixth-form colleges and further education colleges, but the exam board does not break down whether these institutions are fee-paying or academically selective.

However, in 2007 the proportion of private and grammar school pupils taking the exam was even higher, although the number of entries for the exam was also higher. Of 1,648 entries from schools, 27.6% were from grammars and 14.1% were from fee-paying schools.

Michael Gove, the education secretary, announced on Wednesday that the teaching of ICT (information and communications technology) and computer science in schools would be dramatically overhauled, with the existing programme of study scrapped to make way for new lessons designed by industry and universities.

The existing curriculum in ICT has left children "bored out of their minds being taught how to use Word and Excel by bored teachers", he said. He laid out plans to create an "open source" curriculum in computer science by giving schools the freedom to use teaching resources designed with input from leading employers and academics, in changes that will come into effect this September.

Bill Mitchell, director of the BCS, said he was not surprised by the figures from AQA. "Pupils in the state system have been taught computing in a boring and demotivating way," he said. "Why should they want to continue their studies? Private schools may be able to be more imaginative and have more resources."

Simon Peyton-Jones, a computer scientist at Microsoft Research who campaigns for more schools to teach his subject, said that the fact there had not been a GCSE in computing until 2010 was likely to have deterred many pupils from taking AQA's A-level.

"Pupils may have taken a GCSE in ICT, but this would not have prepared them for the AQA computing A-level," he said. "There hasn't been the progression route that encourages and prepares pupils to do this A-level." He said it was possible that fee-paying and grammar schools might encourage their pupils to try out the AQA A-level more than comprehensives.

As part of the AQA A-level in computing, pupils are required to show they can use coding to solve problems, are able to use algorithms and have a good understanding of computer hardware and software.

John Lazar, chairman of Metaswitch, one of the leading communication software companies in the UK, said that Britain's engineering "fraternity" needed to sell itself better to young people. "If you are a bright kid born in Silicon Valley in the US, you end up at Stamford or Berkeley and you aspire to work for Google or Apple or a start-up tech company," he said. "Here in Britain, the brightest graduates feel the force of the City, but they don't feel the pull of engineering. We need to make sure young people understand that there are incredibly exciting opportunities in engineering and software engineering in particular."

The figures show that the proportion of girls sitting the exam is falling. Last summer, just 6.5% took the exam, compared to 8.2% in 2007.

Three exam boards offer an A-level in computing, AQA, OCR and WJEC. These exam boards and one other, CCEA, also offer an A-level in ICT.