Leaked documents show A-level maths candidates had to score just 55% to get an A grade in this year’s paper.
Documents revealing the grade boundaries for all A-level exams set by Pearson-owned exam board Edexcel, have been leaked on social media.
Pearson said all exam boards shared grade boundaries with schools in confidence to help them prepare for results day.
A-level students are due to get their results on Thursday, 15 August.
New maths exam
The leaked Edexcel document, first reported in the Daily Telegraph, also shows biology A-level candidates needed 56% (167 marks out of 300) to get an A, while physics students needed just 59% (176 out of 300).
In English, candidates needed 69% (208 marks out of 300) to get A and 67% (202 out of 300) for an A in chemistry.
This summer is the first time that grades for new-specification A-level maths are being awarded to the vast majority of students.
The exam was reported by students to be very challenging, but the exam board had said before the leak emerged that it was clear the paper was of an appropriate standard.
Exam boards set grade boundaries once all the results are in.
They take into account the predicted achievement levels of the cohort taking the exam and the difficulty of the paper, in an attempt to keep standards the same from year to year.
Responding to the leak, a spokesman for Pearson said: “Our systems are working as they should and the information was shared today via a password-protected, secure website.
“Boards do ask schools not to share this widely to avoid unnecessary stress for students awaiting their results.
“Schools are trusted to treat the info confidentially on behalf of their students and the vast majority do.”
General Secretary of the Association of School and College Leaders Geoff Barton said: “We are extremely disappointed if grade boundaries have been leaked ahead of results day.
“The problem is that anxious students will pore over this information trying to work out what this means for their results.”
He added that this was a pointless exercise because grade boundaries are set to account for differences in the difficulty of papers so that students are not disadvantaged from one year to the next.
“We would urge students against losing sleep over grade boundaries and to wait for their results tomorrow.”