GCSE results for England, Northern Ireland and Wales have improved at all grades for the first time since 1996.
The results trend over recent years: improvements in higher grades
The overall pass rate rose from 97.6% of the exam entries to 97.8%.
And 61.2% were awarded the higher grades, A* to C, up two whole percentage points on last year - the biggest rise since 1992.
But concern has been expressed about the decline in entries for modern languages, and whether GCSE students have essential basic skills.
The council, the umbrella body for the main seven exam boards, said the decline in modern languages - which had been predicted - was "much to be regretted".
John Dunford of the Secondary Heads Association called for an urgent government review.
FULL COURSE GCSE RESULTS
Entries: 5.74 million (down 2.4%)
Pass rate: 97.8% (up 0.2)
A*-C grades: 61.2% (up 2)
A*/A grades: 18.4% (up 1)
A* grades: 5.9% (up 0.3)
Experts suggested the pattern of higher grades and lower entries was accounted for by weaker students switching out of languages and also the double science GCSE.
As usual, overall, girls outperformed boys and students in Northern Ireland achieved higher grades than those elsewhere.
Vocational GNVQs as a whole attracted 4.2% more entries even though they are being phased out. Pass rates were up from 76.2% in 2004 to 79%.
GCSE GRADES A*-C
Northern Ireland: 71%
All boys: 57%
All girls: 65.2%
They are being replaced with various qualifications, including new Applied GCSEs which attracted almost 40,000 more entries this year, a third more than last year.
The pass rate was 93.1% and 39% got grade Cs or above.
'Focus on basics'
The Institute of Directors said its members were "crying out for improvement" in basic skills.
Its head of business policy, Richard Wilson, said: "The starting point for employers recruiting staff is surely to have access to candidates with basic literacy and numeracy skills.
"If individuals lack these skills, workplace training and development or progression into further and higher education becomes much more difficult."
And the man who headed the government's inquiry into 14 to 19 learning in England, Sir Mike Tomlinson, said GCSEs were "failing a generation" on the basics.
Schools Minister Jacqui Smith said: "We are reforming the GCSEs and in the future we will be judging schools on the extent to which pupils are getting not just five good GCSEs but five good GCSEs including English and maths.
"So yes there's more that we need to do. We're already working on it with employers."
The reforms involve revamping English and maths to ensure higher grades do involve functional skills.
The government's white paper said it would be 2008 before the revised English GCSE was available for teaching, with maths a year later.
Chris Keates of the NASUWT teachers' union said business leaders were "practised serial detractors".
The results relate to the performance of exam entries, not candidates.
Last year GCSE performance seemed to have levelled off
First statistics on candidates' performances - such as how many got at least five good GCSEs - are due in October.
The improvements in exam grades will not necessarily mean they have done better.
In 2003, for example, more GCSE exam entries were awarded grades A* to C, but the proportion of students in England achieving at least five of them fell - for the first time since the qualification's introduction.
Last year it was at the same level as in 2002 even though, again, more exam entries got the top grades.