Teenagers in England, Wales and Northern Ireland are due to receive their A-level results, with experts predicting pass rates are set to stall.
In an attempt to tackle grade inflation, regulator Ofqual has told exam boards they will be asked to justify results that differ wildly from previous years.
It means that the proportion of students awarded top grades is unlikely to increase greatly from 2011 levels.
It is estimated that around 8% of exams will achieve an A*, while more than one in four exams will score at least an A - the same as last year.
This year's students will also be the first to face higher tuition fees of up to £9,000 a year.
Many of the hundreds of thousands of students waking up to their exam results will be hoping to make the grade to secure a place at their university of choice.
However, changes to the admissions process means universities will be able to admit as many students as they like who achieve the top grades of two As and a B, or higher.
It means they will be able to offer last-minute places to those who do better than expected and meet this threshold.
Brian Lightman, general secretary of the Association of School and College Leaders (ASCL), said: "When you are talking about those sorts of high grades, A and two Bs, people scoring those sorts of grades - for those to be disheartened would be a tragedy and we must do everything we can to enable them to get their place.
"My advice to students would be don't give up, to look at the options that are open, and there are still plenty of opportunities out there."
