The a-level pass rate in Wales has dropped for the first time since the qualification was reformed ten years ago, according to figures released yesterday.
This year the overall pass rate (for A*-E grades) was 97.1 per cent, down 0.5 per cent on last year.
The pass rate has risen steadily every year since Curriculum 2000 was introduced a decade ago, when it stood at 92 per cent.
The figures appear to bear out the view expressed widely last year by examination experts and teaching unions that Wales had reached the "glass ceiling" in terms of results.
Wales's A-level students also underperformed compared to their English counterparts in terms of the new A* grade, with only 6.5 per cent of Welsh students gaining the new top mark, compared to 8.1 per cent of students over the border.
Gareth Pierce, chief executive of the WJEC exam board, insisted it was still a "very pleasing result".
"Given the influence of the independent school sector in England, where a comparatively larger proportion of A* grades was obtained than in the maintained sector, Wales's results compare very well," he said.
However, Mr Pierce admitted the widening gap at the top would spark concern from Wales's education community.
He said: "As soon as further analysis of the data is completed, WJEC will be keen to explore priorities for the future with partners involved in supporting 16-19 learning in Wales."
There was also a slight decline in the proportion of students gaining A grades, from 25 per cent last year to 24.4 per cent this year.
The total number of A-level exam entries in Wales this year was 37,315, down 2.9 per cent from the number entered last year.
The WJEC said that this was in line with the fall in the population of the age group, and was reflected in decreases in the number of entries for some popular subjects including English and history.
The skills-led Welsh Baccalaureate qualification continues to grow in strength, with 81 per cent of those completing the course being awarded the advanced diploma - equivalent to an A-level A grade - this year, up from 80 per cent last year.
Leighton Andrews, the education minister, said the increase demonstrated that the Bac was quickly becoming embedded as the "pathway of choice" in Wales.
But despite yesterday's results, there are widespread concerns that hundreds of Welsh students could fail to find a place at university because of a significant reduction in the number of places available.
Last week Aberystwyth University and Trinity University College Carmarthen said that for the first time they would offer no places through clearing.