One-third of students in their first year at high school are taught maths by a teacher who isn't qualified in the subject, a report released today says.

While New Zealand's teaching profession was highly qualified - 86 per cent have at least bachelor's degrees - teachers were not always qualified in the subjects they taught.

This was highlighted in a New Zealand Initiative report that details concerns about the link between teachers' and students' mathematics ability.

"While it is difficult to measure the quality of the teaching work force, experience dictates that New Zealand has some excellent teachers, but too many ineffective teachers," the report says.

New Zealand Initiative, an independent public policy think tank supported by chief executives of some of the country's major businesses, published the report by fellow, Rose Patterson, and John Morris, who was headmaster of Auckland Grammar School for 20 years

Nineteen per cent of teacher vacancies in secondary schools were for maths and Patterson said schools' inability to attract high quality maths teachers was to blame.

The report also highlighted the decline in teachers' status which coincided with a slip in their morale.

Teacher morale in secondary schools plunged from 70 per cent in 2009 to 57 per cent in 2012.

Low morale meant the number of people training to become a teacher and the quality applying had dropped.

"That has a serious long-term impact," Patterson said.

The Ministry of Education has welcomed the report and agreed there needs to be a renewed focus on the "quality of teacher preparation".

Deputy secretary for student achievement, Rowena Phair, said a new post-graduate level teaching qualification, available at three universities from next year, was a response to quality concerns.

Funding to improve teacher morale had been addressed by the ministry in this year's budget and an emphasis on professional development would focus on maths.

Post-Primary Teachers' Association president Angela Roberts said principals weren't being swamped with a huge choice of teacher graduates, particularly in maths, science and technology subjects.

The attractiveness of the profession had subsided and the market offered more enticing opportunities for maths graduates than schools could, she said.

Labour education spokesman Chris Hipkins said Education Minister Hekia Parata's war on teachers had caused "plummeting morale and is stopping our best and brightest from joining this critical profession".

The report noted schools were "losing talented teachers because Government reforms have exhausted teachers and yielded very little progress", he said.

"That is because the opinions of teachers have not been respected and their professional development has been largely ignored," he said.