Overall 20.7 per cent of grades were at A+ or A, an increase of 1.2 percentage points on last year.
More than 65.7 per cent were at grades A+ to C, up from 63.3 per cent last year.
The rises come despite the number of entries dipping to a five-year low.
There were more than 5.6 million entries this summer compared with 5.8 million in 2007.
The Joint Council for Qualifications, who released the national GCSE results today, said this was due to a decrease in the number of 16-year-olds and evidence of pupils being entered early for GCSE English and maths.
There was a massive slump in the numbers of pupils taking information technology - with entries down by more than 14,000.
Modern languages also took another hit, with French and German both suffering drops in entries. French was down by 6.8 per cent on last year while German fell by 5.4 per cent.
There was also movement in science entries, which officials put down to changes to the science curriculum.
This year the science double award has been abolished and replaced by two separate qualifications, science and additional science.
Today's results showed that fewer candidates were taking additional science than previously took the double award.
But there were increased entries in the separate sciences, with biology up by 35.3 per cent, chemistry up 29.4 per cent and physics up 29.1 per cent.
There were also small improvements in English and maths results this year.
The overall pass rate for the proportion of teenagers scoring at least a grade G rose by 0.4 percentage points this year to 98.4 per cent.
Jim Sinclair, director of the JCQ, said: "Once again, we have seen a welcome increase in results at GCSE despite the lowest entry for five years. This is evidence of the hard work of the students and the continued dedication of their teachers.
"The core subjects at GCSE continue to dominate and still account for almost half of the full course entry."
Dr Mike Cresswell, director general of the exam board AQA, said the reason for the fall in exam candidates was partly due to a drop in the number of 16-year-olds across the country.
But he said students seemed to be focusing on fewer GCSEs which could also explain rising grades.
"Some young people are focusing their efforts on fewer GCSEs. That has been a trend that has been happening since 2003."
He said the average number of GCSEs taken per student had fallen from just over eight in 2003 to just under eight this year.
Another contributing factor was an increase in the number of students who took English and maths exams early, in November, and are not included in today's figures.
Dr Cresswell said the fall in candidates taking French and German suggested those languages were losing popularity, compared with Spanish, which has seen entries rise.
But he added that grades in French and German were increasing which suggested a select group of "motivated and talented" students were choosing those courses.
Changes to science exams have increased the number taking single science which looks at biology, chemistry and physics in less depth than studying them singularly.
Dr Cresswell said the number completing additional science. Which replaces double science, had dropped, but pass rates improved, again suggesting those who took the exams were better suited to the subject.
The North East, which showed the smallest increase in A-level results last week, had reason to celebrate today.
A regional breakdown showed the region had the greatest improvement in C grades, of 11.3 per cent.
It also had the second biggest improvement in A grades, 5.3%. Only London saw a greater increase, 5.5%.
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