Just over half marks were needed to score an A grade in A-level maths this summer, according to leaked documents.
Grade boundaries for Edexcel's maths A level show students who gained 165 out of a possible maximum of 300 marks (55 per cent) will be awarded an A.
Last year, 184 marks (61 per cent) were required for the same result.
A-level results: How to help students through clearing
The documents also show that this summer, 43 marks (14.3 per cent) would result in an E grade - considered a pass.
The grade boundaries have been leaked the day before sixth formers across England, Wales and Northern Ireland are due to receive their A-level results.
In a statement, Edexcel's parent company Pearson said that grade boundary information is shared with schools a day in advance to help teachers prepare and that the information was shared via a password-protected, secure website.
The leaked boundaries also show that 72 per cent of marks were needed overall for an A* in the maths A level this summer, along with just over a third of marks (34 per cent) for a C grade.
The figures relate to overall Edexcel grade boundaries for the new specification maths A level.
Maths is one of the last subjects to be reformed as part of a major overhaul of exams in England.
This summer is the first time that grades for new specification A-level maths are being awarded to the vast majority of students.
Last year, just a small number of students took the reformed qualification - those who sat the exam after completing the course in just one year, rather than the usual two.
A small number of students may still be studying the old "legacy" maths A-level course.
The leaked documents also give grade boundaries for all other Edexcel A-level qualifications.
Edexcel is one of England's largest exam boards.
A Pearson spokeswoman said: "Per JCQ guidelines, all boards share grade boundary info with schools a day in advance to help teachers prepare and support their students better on results day.
"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."
Geoff Barton, general secretary of the Association of School and College Leaders, urged students "not to lose sleep over grade boundaries".
"We are extremely disappointed if grade boundaries have been leaked ahead of results day," he said.
"The problem is that anxious students will pore over this information trying to work out what this means for their results.
"This is a pointless exercise because grade boundaries are set to allow 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."
There were reports earlier this year that some students were complaining that one of the new Edexcel A-level maths papers was too hard.
In a video statement last week, Pearson addressed these concerns, saying it was aware that some had found Paper 2 "more difficult than they were expecting".
The board said it wanted to reassure students that independent experts had analysed the paper and confirmed it was a "fair and valid exam testing across the ability range and the course curriculum".
This summer, questions from one paper of Edexcel's new A-level maths qualification were leaked ahead of students sitting the exam.
A police investigation is ongoing.