Thousands of students will collect their A-level results today, amid suggestions of a slight increase in the number of top grades being awarded and warnings of "greater volatility" in marks.
Analysis of the entry levels for the traditionally top-scoring subjects, such as maths, indicates the percentage of students achieving an A or A* will increase.
And the number of boys achieving the very top grade could pull further ahead of girls due to a rise in take-up of maths - typically a high-scoring subject - according to Professor Alan Smithers, director of the Centre for Education and Employment Research at Buckingham University.
Last year, boys held a 0.9% lead over girls at A* grade, although girls had a 0.4% lead at A and A* grade combined - having out-performed boys every year since the millennium.
Entries to maths and further maths in England are up again, with the former now overtaking English as the subject with the highest intake.
Since they award by far the most A* grades, this could lead to an increase in A* grades overall.
Prof Smithers said that the gap between boys and girls had been narrowing since 2006, and that boys could "go further ahead this year due to the increase in people taking maths and further maths".
Yet students are bracing themselves for greater volatility in this year's results because of changes to the curriculum, a teachers' union has said.
Chris Keates, general secretary of the NASUWT union, said that teachers and students had struggled to get to grips with new syllabuses which were brought in this year and could impact results.
The Government introduced changes to the subject content of all AS and A-levels last year. Mid-course exams were also scrapped, meaning that all exams are now taken at the end of the year.
Ms Keates said the changes would particularly affect those receiving their AS-level results, as they are the first group to go through the new curriculum.
"Students and teachers have had a very short timescale to get to grips with the new syllabuses, particularly at a time when they have been trying to prepare for the introduction of revised A-level courses from next month," Ms Keates said.
She also said budget cuts have affected staffing levels and resources in schools and colleges, adding to the challenges for students.
"Young people have continued to excel despite these challenges which have been compounded for many by the Government's removal of financial support for the most disadvantaged students and its cuts to the system of independent careers advice and guidance.
"Tomorrow offers an opportunity to celebrate the talent of our young people, but should also provide pause for thought about the increasing barriers that students and schools are facing to achieve this success."
Russell Hobby, general secretary of school leaders' union NAHT, warned there could be "significant variation" in the results, with many students getting grades they had not expected.
He said that while the national picture may look "stable", the changes to the curriculum and examinations meant there could be big differences at a school and student level.
"For individual students, teachers and schools this is a real concern," Mr Hobby warned.
"We are also concerned about the possibility of a further dip in the number of students taking creative subjects at AS and A-level."
Anne Longfield, children's commissioner for England said: "I'm delighted to congratulate the thousands of students across England who received their A-level results today and to wish them the very best for the future as they go on to further develop their skills and knowledge and follow their chosen paths.
"The results clearly demonstrate how much young people are capable of achieving.
"I very much hope that those who didn't achieve the results they wanted get the support they need to help them to continue to realise their ambitions."
A Department for Education spokeswoman said: "A-level results day is the culmination of months of hard work for students and teachers and everyone involved deserves credit. Our exam and curriculum reforms will build on those achievements and ensure pupils have the knowledge and skills that will help them secure a university place, apprenticeships or a great job.
"Content for all the 2015 A-level subjects was published in April 2014 following extensive consultation with the education sector which began in May 2013.
"Our changes to AS and A-levels mean young people have the time to develop the knowledge and understanding they need to master their subject without the sixth form years being dominated by continual exams. This is precisely what universities have been asking for."