The last NCEA exams of 2016 were held today, wrapping up the school year for thousands of senior secondary school students.
This year's exams were disrupted by earthquakes and, to a lesser extent, flooding in the lower North Island.
A spokesperson for the New Zealand Qualifications Authority said schools had until 9 December to seek derived grades for students who had missed exams or whose performance was impaired.
Wellington Girls College acting principal Jo Kahl said the grades would be based on mock exam results and some students would wish they tried harder in those assessments.
"One of the things that as teachers were reasonably pleased about is that next year we'll certainly be emphasising with students the importance of taking those exams seriously, and not taking them lightly at all.
"But the best grade goes through as far as the students are concerned so they shouldn't be too disadvantaged."
Ms Kahl said students had shown great resilience in coping with the earthquakes.
Some schools said they would use derived grades for all students who had exams in the days immediately after the 14 November earthquake, which forced schools to close and cancelled exams in some areas.
The authority said NCEA results would be released on 17 January, with Scholarship results out on 8 February.