Nearly half of Year 12s could fail the new secondary school qualification under a worst-case scenario.
Education Ministry estimates in documents obtained under the Official Information Act (OIA) by the Post Primary Teachers Association (PPTA) ranged from an optimistic failure rate of nearly 30% at Year 12 and a pessimistic estimate of about 45%.
Both figures were well above the current failure rate of more than 15% for Year 12s attempting NCEA level 2.
The Education Ministry said the estimates had significant limitations and would be mitigated by measures, including training for teachers.
"As part of policy development, the ministry undertook early scenario-based modelling to explore possible outcomes to help inform implementation planning. These figures are not a forecast or prediction of future attainment rates," it told RNZ in a statement.
In a letter accompanying the OIA response to the PPTA it said: "It is common to see a dip in achievement rates with a change that is intended to strengthen the credibility and robustness of a qualification, and this is also seen in other countries. You will note that the paper also identified opportunities, based on the experience of previous changes, to reduce the risks to attainment rates. The policy decisions made by Cabinet about the new qualifications took this into account, and mitigations have been put in place to support student success."
Education Minister Erica Stanford told RNZ it was the ministry's job to assess potential impacts, and the government's job to provide support so students succeeded.
"We have deliberately required students to pass three subjects rather than four to gain the new qualification, provided an additional year of lead-in time, and are making significant investments in support," she said in a statement.
The support included maths and writing acceleration programmes, extending maths resources to Years 9-10, targeted support though the Pasifika Secondary School Tutoring Programme, and professional training for teachers.
"For too long, NCEA has allowed students to accumulate credits without necessarily demonstrating the knowledge and skills their qualification should represent," she said.
"We make no apologies for raising standards. But higher standards must come with the support students need to meet them, and that is precisely what we are delivering."
The PPTA said the ministry's optimistic estimate would result in about 10,000 more teens failing to get a qualification at Year 12 and the pessimistic rate in 19,000 more.
The document estimated the Year 13 failure rate could rise from the current rate of about 15% for attainment of NCEA level 3 to about 25% in the best-case scenario or about 35% in the worst case with the new certificate.
The estimates assumed students who achieved 14 credits in a subject in NCEA would also pass that subject under the new qualification.
The document said the modelling was based on subjects that used achievement standards because industry-led vocational subjects did not exist yet.
The estimates were first made in 2025, but repeated in April this year to compare pass rates for a qualification requiring three subject passes and one requiring four subjects.
The four-subject option had even worse pass rates and was dropped.
The ministry said the estimates should be interpreted with caution due to significant limitations in the modelling approach.
"The estimates used current NCEA achievement data and predictions about how students, schools and teachers might respond to the new qualification requirement. As the paper notes, these were initial, rough estimates and are indicative only, as they depend on predictions of future behaviour," it said.
But one of the ministry's documents said even with potential mitigations the risk of high failure rates remained.
"However, the modelling still indicates that the risk of decreased attainment for at least the first few cohorts could be high, as they will not have had the full benefits of the new curriculum and additional supports. Longer-term, there will still continue to be students who face barriers to attainment, some of which are outside of the education system (as there are under NCEA)," it said.
The documents said the changes could prompt some students to disengage from school earlier.
Earlier this year, RNZ revealed 19% of last year's school-leavers had no formal qualification at all - one of the highest figures on record since NCEA was introduced.
The ministry said mitigations included phasing in the new qualification from 2028 to 2030, aligning it with the new curriculum, training and resources for teachers, and advisory groups to identify problems early.
PPTA president Chris Abercrombie said the government talked about mitigations, but teachers were yet to see any action.
"When I talk to teachers about the curriculum right now, they're not feeling like it's resourced ... so we've pretty much got no confidence in the mitigations that the minister and the ministry are talking about," he said.
"I talk to English and maths teachers and I go, 'hey, how's that professional development that I've been told you're getting?' and they look at me like I've grown a second head.
"If we want to make these changes, and if the government wants to make these changes, they have to be effectively resourced and effectively resourced from now with a clear plan, not just, 'hey, we've got this, we've got the vibes'. At the moment, the minister just seems to be going on vibes."
Abercrombie said the documents showed the effect would be greatest on students in poor communities, meaning the government's policy would "be running the equity gap on steroids".
Asked if a higher failure rate was inevitable with a qualification that was intended to be more demanding than NCEA, Abercrombie said a qualification should show what students could do, not what they couldn't do.
"Sure, more students will not achieve, they'll fail, but we need pathways for them and we haven't got that," he said.
"We just can't throw on the junk heap hundreds if not thousands and thousands of students."
The modelling indicated the third of schools serving the poorest communities could see their Year 12 qualification attainment rates plummet from about 75% to just over 50% in the optimistic scenario and to about 25% in the pessimistic scenario.
For that group of schools, Year 13 attainment could drop from nearly 80% to about 55% in the optimistic scenario or about 35% in the pessimistic scenario.
The documents showed the government considered options for the number of subjects required to gain the new certificate.
The government last year said students would have to pass four subjects, but this year reduced that to three.
The document said three subjects would be easy to understand and reliable, though it might not be clear what students who attained the qualification could know and do.
It said students might focus on just three of the five subjects they studied but there was strong incentive for coherent, deep learning.
The document said requiring three subjects for the qualification carried fewer equity risks than requiring four subjects and was "effectively equivalent to the status quo".
Overall it said three subjects was: "Likely to be motivational, credible and easy to understand, and has lower risks to post-school outcomes, but some may see it as not aspirational enough."
