Three in 10 A-level entries scored at least an A grade this year as Northern Ireland students performed strongly.
Figures showed 30.4% received grades A* or A, an increase of 0.9% percentage points on the previous year.
The gap between girls and boys widened as, for the first time, the latter’s results slumped when compared across all grades.
Despite a year of major change to the qualification, performance remained stable, said awarding organisation the Joint Council for Qualifications (JCQ).
Chief executive Justin Edwards said: “There are reforms and changes going on within the A-level system so to have stable outcomes ... is important and I am pleased that Northern Ireland candidates continue to do strongly.”
He said there was plenty of “head room” for further inflation in grades in the years ahead without hampering universities’ ability to choose between pupils.
The “decoupling” of AS-levels from A-levels in England, entailing a move away from coursework and modular exams throughout the course, has seen a drop in the number taking AS-levels in Northern Ireland.
A proportion of the qualifications there come from English awarding bodies.
The gap between girls and boys widened across all grades.
Mr Edwards said this was due to an increase in outcomes for girls and a decrease for boys.
Girls now outperform boys by 1.5 percentage points at the A* grade and 6.5 percentage points at A*-A.
The chief executive added: “For a first year we have boys’ outcomes decreasing and girls’ outcomes increasing well and strongly so we need to keep an eye on that.”