An algebra exam last week was far too hard for the 15 and 16-year-olds who were sitting it, according to the Wellington Maths Association.
The test was the first of a series of maths exams for NCEA Level 1, but the association's president, Bruce Welsh, said it had a level of thinking above the level of the students who had to sit it.
Mr Welsh said his members were angry at the way the test was set.
"We have had responses from over half of the schools in Wellington and the Wairarapa, saying it was not appropriate for Level 1," he said.
"A lot of the teachers are saying it has killed the confidence of the children and of the teachers as well.
"They are not sure what to expect in an exam."
Secondary Principals' Association president Sandy Pasley agreed, saying maths teachers through New Zealand had expressed concern about this exam.
"It was different from last year's [exam] and some of the students came out of the paper and found the difference quite upsetting.
"That happens, of course, but there was a change of emphasis from a skills-based exam to an investigative one.
"That can be really good but it requires time to think about how to answer the questions, and, when you have got a set amount of time like one hour, then it can be very challenging."
The New Zealand Qualifications Authority agreed the exam aimed to get students to use maths concepts to solve algebraic problems, rather than simply answering straightforward skills-based questions.
It said this exam was developed by an experienced team and reviewed by several current teachers, and exams had been trending this way for several years.
But it said it could and would adjust the marking schedule for an exam if it found a question was more difficult than expected for students.
This would be part of a benchmarking exercise that was done within days of every exam.
The authority said it was standard practice to make sure all student work was marked fairly and was in line with previous years, so no student was unfairly advantaged or disadvantaged.
The exam was the first in a series for NCEA Level 1.