Pupils will not be penalised even though moderators disagree with almost quarter of internal assessments.
Thousands of school students are being awarded the wrong NCEA grades, a review of last year's results has revealed.
Nearly one in four grades given by teachers for internally marked work were deemed incorrect after checking by New Zealand Qualifications Authority moderators.
Students found to have a flagged grade will not have it changed - but authorities have told the Herald they are comfortable with the system.
"We can assure students and parents they can have confidence in the comprehensive moderation process," said Richard Thornton, NZQA's deputy chief executive.
"There is always the potential for there to be some disagreement. A good example of this could be in the assessment of an art portfolio where interpretation can influence the final judgment."
Internal assessments are set and marked by teachers, with grades checked by other teachers and samples in turn checked by NZQA.
Last year, 2000 internally assessed standards across 356 schools were picked for moderation.
A moderator reviews a student's work and considers if the teacher has correctly judged whether the work has achieved or not achieved the standard.
Last year, the agreement at the level of grade was 76 per cent - meaning moderators disagreed with almost one in four grades awarded.
In 2012 the rate was 80 per cent, and in 2011 86 per cent - although a change in how work for moderation is collected means comparisons with previous years are limited.
Mr Thornton said internal assessment was based on an overall teacher judgment and included a large number of factors which were all taken into account by moderators.
NZQA expected the agreement rate to improve, he said.
Over the past three years a large number of new standards had replaced older ones, which meant teachers had to get used to assessing them.
Allan Vester, chairman of the Secondary Principals' Council and head of Edgewater College in Pakuranga, said it was also important to realise disagreement would be on work at the margins of grades.
However, Avondale College principal Brent Lewis - who has been a critic of NCEA despite about 80 per cent of his roll opting for it over Cambridge - said the rate was troubling.
"It is clearly disappointing and obviously there is more work to be done."
The overall integrity of NCEA is overseen by an independent advisory group, the Technical Overview Group Assessment. Its chairman, Emeritus Professor Gary Hawke, has recently said the public can have confidence in NCEA and its moderation process.
Post Primary Teachers Association president Angela Roberts said that independent overview should provide reassurance.
Many overseas jurisdictions had no moderation between schools at all about levels of attainment.
Read the full NCEA report here: