Concerns were raised about the educational divide across England tonight as A-level results soared to a record high. Figures released by the exam boards highlighted startling discrepancies in grade A passes in regions around the country.

Overall figures showed the national pass rate has risen above 97% for the first time this year, while one in four sixth-formers were awarded A grades (25.9% up from 25.3% last year). For the first time the exam board released a regional breakdown, examining pass rates and the proportion of students getting A grades in various areas of the country. It showed the greatest improvements in the last six years have been in the South East while the North East appears to be lagging behind.

While the South East has seen A grades rise 6.1% - to 29.1% since 2002 - the North East has seen an improvement of just 2.1% - to 19.8% in the same period.

Shadow children's secretary Michael Gove said the divide was "worrying". He said: "It underlines yet again the need for reform to create new good school places so that children in the less well-off areas get the same opportunities as others."

Liberal Democrat schools spokeswoman, Annette Brooke, said there was a "clear divide" at the heart of the education system. Schools Minister Jim Knight said more analysis would be needed before "significant" conclusions could be drawn.

Dr Mike Cresswell, director general of the AQA exam board, said the regional breakdown showed a "long-standing historical pattern".

"There will be all sorts of explanations for the differences and they won't all necessarily lie in the education provision in the regions. The things that affect how young people perform in school are many and varied," he said.

Around the country teenagers were celebrating their successes as many discovered they had the grades to secure university places. And they won plaudits from politicians and teachers' unions for their hard work. Mr Knight offered congratulations and said the results were a "tremendous tribute" to the effort put in by students, supported by parents and teachers.

He added: "They also show a good return on a decade of record investment and policies which have encouraged more young people to continue and achieve in education."

Christine Blower, acting general secretary of the National Union of Teachers, said the results were a "ringing endorsement" of high quality teaching standards and student attainment.

The National Association of Head Teachers (NAHT) said it was particularly pleased with the rise in the number of students gaining A-levels in maths and science.

Chris Keates, general secretary of the NASUWT teachers' union, said: "These are Olympian achievements and represent years of hard work and sustained effort by students and teachers alike."

The national figures showed there were a record 827,737 A-level entries this year. Traditional subjects were still firm favourites with English and maths the top choices for students - and the numbers of maths candidates rose from 60,093 last year to 64,593 this year.

Dr Cresswell said: "There was an upward trend that began a couple of years ago that has accelerated. There are more candidates doing mathematics than at any time in the past. It's important we have people with high mathematic skills so that has to be good news."

Mr Knight said: "It's crucial for society that we have talented mathematicians and maths is essential for science and innovation - today's A grade mathematicians will soon be solving the problems of tomorrow."

Entries in biology and chemistry were at their highest levels for a decade and the number of physics candidates also rose.

Fears that languages would see a slump in popularity proved unfounded as the number of candidates taking A-levels in French rose to its highest level since 1993. Spanish entries were the highest they had ever been at 7,055.

As the results were revealed, ministers announced plans to reform the system, with the introduction of the extended project which will be worth half an A-level and is designed to help prepare students for work or university. Mr Knight has called for every school to offer it to pupils alongside other qualifications. Projects include making a film or model, solving mathematical problems or writing essay-based investigations.

And from next month the new A* grade will be introduced at A-level, aimed at helping universities identify the brightest students. The first A* grades will be awarded in 2010.