Education experts are blaming everything from poverty to student loans for New Zealand's poor performance in the OECD's international test of 15-year-olds in reading, maths and science.
More than 500,000 15-year-olds, including 4000 New Zealanders, sat two-hour pen and paper tests last year. Thirty-four OECD countries participated, as did 31 other countries and economies including Shanghai and Hong Kong.
The tests aim to find out if students can apply their knowledge of reading, maths and science and include multi-choice questions and more open questions.
New Zealand's scores in reading, maths and science examined by the Programme for International Student Assessment (PISA) in 2012 have fallen since the previous test in 2009.
Formerly among the top-performing OECD nations, New Zealand is now outside the top 10 countries in reading and science, and barely above the average in maths. In countries previously ranked below New Zealand, scores improved or declined only slightly. That was enough to push New Zealand from seventh to 13th in reading, seventh to 18th in science and from 13th to 23rd in maths.
The drop has happened under the National-led government, but it is blaming an accumulation of factors it says it found when it took over the education portfolio in 2008.
However, teacher unions say the Government is to blame, and should have invested more in poor communities.
The Principals' Federation said behaviour problems have had an impact, while Secondary Principals' Association president Tom Parsons said the curriculum teaches too many subjects and schools need to focus on the basics.
"One could argue the richness of our curriculum - which is extremely rich compared with many of the other nations that are going up on the PISA scale - it could be a handicap. And maybe we've lost the goal with the richness of that curriculum in that we haven't concentrated on the bread and butter."
Mr Parsons said he is confident that the national standards in reading, writing and maths will ensure better results when the test is held again in 2015.
PPTA president Angela Roberts told Radio New Zealand's Morning Report programme on Wednesday that quality teaching can push back only so much against impoverished backgrounds, and advice given to the Government in 2009 about what was needed was ignored.
Principals' Federation president Phil Harding said the OECD report highlights New Zealand's disciplinary climate and level of truancy as having a significant impact on achievement. He said those things are triggered by circumstances beyond the school gate.
But a professor of education, John O'Neill, said there might be no drop at all, and it is possible that the questions in the latest test simply did not suit New Zealand students.
Long-standing problems, says minister
Education Minister Hekia Parata said the Government found long-standing problems in the education system when National came to power and has been working to fix them.
Ms Parata said the 15-year-olds tested in 2012 had been in the school system since 2000 and a range of factors would have influenced their education.
These included the introduction of a new curriculum in 2007, an increase in teacher numbers without a matching increase in the budget for in-service training, and schools reporting difficult student behaviour. The Government had also introduced the National Standards.
Ms Parata told Radio New Zealand's Morning Report on Wednesday the fall is the result of 11 years of problems within the education system that the Government is focused on fixing. She said she has been advocating and promoting the improvements that the OECD recommends.
New Zealand's score in maths fell from 519 to 500, just above the average of 494 and one of the biggest drops in the PISA results. Denmark, Ireland, Australia and the UK had similar scores, while the top mark was 613 in Shanghai.
In reading, New Zealand's score fell from 521 to 512. The top score was 570 in Shanghai. Australia also scored 512. The United States and United Kingdom were close to the OECD average with 488 and 498 points, respectively. Canada was the highest scoring English-speaking nation on 523.
New Zealand's score in science was 516, down from 532 in 2012 and well behind Shanghai's top score of 580. However, New Zealand's score was still above average and the scores of Australia, the UK and Canada also fell.