Students at Jersey's Beaulieu School are among some of the first to gain a grade 9 at GCSE - equivalent to what would have been an A**.
The grading switch is part of wider reforms designed to make GCSEs more rigorous and challenging.
A third of exams taken at the private girls' school were awarded A*or A grades (or equivalent 7-9 Grades).
A grade 7 is broadly equivalent to an A under the old system, while a 4 is broadly equivalent to a C.
It is predicted that many teenagers who would have gained the highest possible grade last year will not do so this summer.