GCSE exams have apparently been tougher this year to counter for the past upward drift, and the target for schools has also been raised.
Glenys Stacey, chief executive of qualifications regulator Ofqual, explains that in the past two decades grades "have raised inexorably".
"Our job is to look that in the face and question why... but it does affect public confidence," she told the Today programme.
"The view from experts and in the public is that it cannot be down to improvements alone, there must be something underlying," she said.
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