Half the attempts at advanced level exams intended to stretch the brightest candidates ended in failure this year.
Tougher questions are to become more mainstream
The failure rate in A-levels in general dropped to 3.8%, prompting further debate about standards.
But in the tougher Advanced Extension Awards it rose to 50.6%, ranging from 25.6% in classics to 74% in psychology.
The government intends to incorporate similar questions into mainstream A-levels as one way of discriminating between the best candidates.
The awards are optional and available in a relatively limited number of subjects.
There were only 9,305 entries in total - compared with 783,878 for A-levels - though this was more than 28% higher than in 2004.
They are graded simply "distinction" or "merit".
The proportion of entries gaining a distinction fell by 1.1 percentage points from last year and at merit level by 0.2.
The proportion failing to attain a grade rose 0.2 to 50.6%.