Nearly one in four GCSE entries could be awarded at least an A grade in what is expected to be another record year of results, it has been predicted.
Around one in 12 exams could score a coveted A*, an education expert suggested.
The predictions come just days before teenagers in England, Wales and Northern Ireland receive their GCSE results.
Last summer, the pass rate rose for the 23rd consecutive year, with 69.1% of entries achieving at least a C grade.
Professor Alan Smithers, of the Centre for Education and Employment Research at Buckingham University, suggested this could reach 70% this year.
And the proportions of exams earning top grades could rise slightly, he suggested, saying: "I would say that on the pattern of previous years we could expect approaching 8% to get an A*."
He added that the percentage achieving at least an A grade could nudge up to 23%. In 2010, 22.6% of exams got an A or A*, while 7.5% were awarded an A*.
Professor Smithers also suggested that this year's results could be affected by the Government's introduction of the English Baccalaureate - awarded to pupils who score C or above in English, maths, science, a foreign language and history or geography.
Students receiving their results next week will have been halfway through their two-year courses when this was brought in, he said.
"It's a case of whether any school changed what they were doing mid-stream. They may have been offering half courses in history or geography and said to students 'you will have to do the full course'".