The proportion of A-level exams awarded the top A* grade unexpectedly rose this year, results released this morning reveal.

Three decades of annual increases in the proportion of students achieving the top grade finally came to an end in 2012, with the percentage of entries awarded top grades also falling last year.

But results from this year’s exams saw the percentage of A* grades awarded rise from 7.6 per cent last year to 8.2 per cent, the highest percentage recorded since 2011.

When A grades are also included, however, the figure dropped for the third successive year to 26 per cent, down from 26.3 per cent in 2013. The A*-E pass rate also went down to from 98.1 to 98 per cent - the first time it has decreased since 1982.

This year’s results come against a backdrop of significant changes for schools. Most notably, no January resits took place in England for the first time in recent years, effectively signalling a switch to linear, end-of-course assessment.

The Joint Council for Qualifications (JCQ), which represents the main exam boards, said overall results were “very stable”, but warned that individual schools could face some turbulence.

“It is possible that due to the removal of the January series some schools and colleges may experience volatility in their results, depending on how they have adapted to the changes,” JCQ director general Michael Turner said.

“But it is important to remember that standards have been maintained and, despite the changes, are comparable with previous years.”

Brian Lightman welcomed the increase in A* grades. “These are excellent results at a time of great change,” he said.

Andrew Hall, chief executive of the AQA exam board, said the increase in A* could have been caused by schools “changing their teaching strategy” and making good use of times previously spent preparing students for re-sits.

An increase in students taking facilitating subjects favoured by the most selective universities could also have been a factor, Mr Hall said, with “savvy students picking the right subjects for them and stretching themselves”.

OCR chief executive Mark Dawe said another reason for the increase could be the trend by universities to include the A* grade in their entry requirements. “It has become a highly important grade,” he said.

Last week, TES reported that headteachers were “hugely worried” about how the raft of GCSE and A-level reforms which came into effect this year would affect schools’ performances.

This year’s cohort of students taking AS-level exams was the first to have been affected by the English Baccalaureate GCSE performance measure. Several EBac subjects enjoyed a surge in popularity, including geography (up 16.9 per cent) and Spanish (up 14.8 per cent).

Boys have widened their lead over girls at A*, but trail behind in second place when A and B grades are factored in, although the gap has narrowed.

This year’s subject choices have also reinforced gender differences. Girls account for 71.8 per cent of English entries, but female candidates make up just 21.1 per cent of those taking physics.

Despite A-level students in Northern Ireland and Wales having still been able to take resits in January, they were outperformed by their English peers in terms of the proportion of A* grades achieved. However when As were also taken into account, Northern Irish students came out on top, with 29.9 per cent of entries achieving one of the top two grades.

In total there were 833,807 A-level entries this summer, almost 17,000 fewer than last year. However, the number of AS-level entries increased by 67,000 in the same period.