Tens of thousands of NCEA papers have been left untouched on exam room desks as students fail to turn up or "forget" to sit them.
In the past three years, about 6.5 per cent of exam papers have been left untouched - in part because some students know they have enough credits to pass without sitting the exams.
There are no penalties for failing to sit NCEA exams.
Teachers from St Patrick's College in Kilbirnie were disappointed some students had not sat their end-of-year exams and, in a school newsletter, said there was no excuse for forgetting, especially in an age of electronic reminders.
Absence figures for this year's exams are still being checked by the New Zealand Qualifications Authority (NZQA), but to date 6.9 per cent of students are known not to have sat NCEA level 2 exams, and 24.9 per cent did not sit scholarship exams last month.
St Pat's head of careers Mike Woods wrote in the newsletter that absent students should re-sit their missed papers or repeat the year in that subject, "but should not advance".
"The massive educational changes with NCEA was to ensure all students had a fair shot at academic success. However, it does not give students the right to opt out." Tools such as Facebook, cellphones, electronic calendars and diaries meant forgetting an exam was not an excuse.
Wainuiomata High School principal Martin Isberg said teenagers would always be strategic about study, whether it was good for their future or not.
He said he had to convince his own daughter - who attends a different high school - to sit her exams, even though she did not need to sit them to pass.
"We talked her into it in the end, but kids are often thinking strategically and they're not in line with our thinking."
Secondary Principals' Association president Tom Parsons said moving to online exams would help fix the problem because students advancing more quickly would get their exams over with earlier in the year.
Over the next eight years, NZQA was aiming to allow students to sit exams online once they have completed credits.
Mr Parsons said not all students would turn up to exams - just as not all adults turned up to work every day - especially if they knew they had already passed.
"I know it's not a good concept, but it's a free choice and some teenagers hate that they're made to go to school. Until a time comes where students and parents recognise they don't get to do just the stuff they want, then this is what we've got to deal with."
Percentage of NCEA exams in which students were absent, by region and year.
Wellington 2011: 5.5 per cent 2012: 5.4 per cent 2013: 5.6 per cent
Wairarapa 2011: 5.9 per cent 2012: 6.4 per cent 2013: 9.3 per cent
Hawke's Bay 2011: 5.9 per cent 2012: 5.6 per cent 2013: 5.5 per cent
New Zealand total 2011: 6.2 per cent 2012: 6.4 per cent 2013: 6.9 per cent
Percentage of NCEA exams for which students were absent this year by exam type
Level 1: 6.1 per cent
Level 2: 6.9 per cent
Level 3: 7 per cent
Scholarship: 24.9 per cent
Figures for 2013 have not taken into account all accepted absences.
- The Dominion Post