Exasperated maths teachers are drafting a letter of complaint after a major exam left baffled students facing questions they had little chance of answering.

For the second year running NCEA Level One maths has hit trouble with questions so difficult even the brightest students struggled.

Teachers say the exam confounded students with duplicate questions, unnecessarily verbose instructions and testing work not taught in the syllabus. It also omitted key topics from previous years.

One Auckland teacher said pupils were angry and upset they couldn't solve problems in the geometry paper, believing it was missing vital angle information in questions. They were also blindsided by a new investigation style of questioning.

One Year 11 student said the exam was "awful" and "impossible".

"At my school we were exposed to the new style of the Tables, Equations paper during our practice exams so we did expect the paper to be like how it was, however geometric reasoning was awful.

"In total, out of about probably over 15 questions, I answered probably two or three like a lot of other people I talked to after. I also know a lot of people just left the paper completely blank."

When it came to the geometric reasoning section, "the questions were extremely difficult, there were angles missing and they made all diagrams very complicated. Talking to other people they did what I tried to do and remember all the angle reasons and circle theorems and try to see which ones fit with the questions but none of them did with the way the questions were laid out which made the paper seem impossible to do.

"All the work we have done throughout the year has virtually gone to waste, which is very disappointing."

One Auckland teacher said pupils were angry and upset they couldn't solve problems in the geometry paper, believing it was missing vital angle information in questions. They were also blindsided by a new investigation style of questioning.

This morning the national qualifications authority stood by the exam, saying it tested students on the math's curriculum and changes had been flagged.

"The New Zealand Qualifications Authority is confident in the quality of the examination, which met the specifications clearly signalled to schools in advance of the school year," said deputy chief executive assessment Kristine Kilkelly.

All NCEA assessments were aligned to the standard and the New Zealand Curriculm. The authority updated assessment specifications annually, which included changes to question format, as was the case in one of three standards assessed in yesterday's exam.

"We provide ongoing communication about examinations through a number of channels including publication of resources about particular standards, including examples of the types of questions that will be asked as was the case for Standard 91028 Tables Equations and Graphs," she said.

"We also send emails and circulars to schools. The change in the format for the examination of this standard were featured in the workshops run by the New Zealand Association of Maths Teachers and supported by NZQA earlier in the year."

An open letter to the Ministry of Education and the New Zealand Qualifications Authority is being drafted by teachers across New Zealand giving critical analysis of all three papers deemed too tough for students taking the first level maths exam.

All three papers - Tables, Equations and Graphs, Geometric Reasoning and Chance and Data - have come in for criticism and some are calling the exam a disaster.

"Honestly, the best thing one can say about this paper is that it seems to have been spell-checked thoroughly," wrote one teacher about the geometry.

Teachers say there was no warning from NZQA there would be changes in the spread of questions and the introduction of a new investigation style of question that up to a third of a paper was based on.

"NCEA seems to be experimenting with a new format for their Tables, Equations, and Graphs paper. But 2017's Year 11 students, do not want to be guinea pigs for a National Certificate that their future schooling and careers will be based off of," wrote Auckland teacher Talia Thomas.

"Level One Maths has proven to be a disaster for the second year in a row. 2016's level one students should consider themselves lucky as they only had one messed up paper, the MCAT. However, this year, the Geometric Reasoning and Tables, Equations, and Graphs papers proved to be extremely difficult for even the brightest of students."

She said most of New Zealand's Year 11 students should not have struggled this much with a maths exam and hoped NZQA realised there was obviously something wrong given the widespread backlash.

Last year there was uproar after a Year 11 NCEA Level One Maths Common Assessment Task (MCAT) proved so difficult students were left in tears.

Then a major error in a Level 3 Statistics exam meant a question could not be answered with an investigation revealing the paper wasn't checked properly before it was published.

NZQA has been approached for comment.