New Zealand's bad results in an international maths and science test are being blamed on factors including grouping children by their ability and the previous government's national standards in reading, writing and maths.
Scores for New Zealand nine and 13-year-olds fell in both subjects in the Trends in International Mathematics and Science Study, with the 13-year-olds recording their worst results ever - 482 for maths and 499 for science.
That was significantly lower than countries New Zealand traditionally compares itself to such as Australia and England where average scores exceeded 500, and the leading nation, Singapore, which scored more than 600 in both subjects.
House of Science science education centre chief executive Chris Duggan said that was a problem.
"We are seeing a trend, and I think it's a worrying trend, where over many years now New Zealand is getting further behind other OECD countries in maths and science achievement for these age groups and I think something needs to change, because if we keep doing what we're doing we're going to keep getting the same results," she said.
Duggan said schools prioritised reading and maths, and science had been a poor cousin for a long time.
"Often science just doesn't get done to the quality that it needs to be even though it is a core curriculum area. It is inherently expensive and difficult to resource and the confidence of the teachers is often not there," she said.
"The Education Review Office reported a few years back that only 27 percent of our primary schools are delivering an effective science programme, which is shocking, and it looks like things haven't improved an awful lot."
Duggan said the government should give schools ring-fenced funding for science so that it could not be used on other subject areas.
She also recommended training more teachers to teach science so that it was a regular part of their classroom day.
The national coordinator of the Association of Primary School Science Teachers, Sandy Jackson, said New Zealand would have a problem if the scores continued to fall.
She said science had been sidelined by schools focusing on reading, writing and maths.
"A few years ago science became a big focus and then numeracy and literacy took over again and science was sort of dropped and a lot of primary and intermediate teachers just don't have the time to do justice to a good science course," she said.
She said many primary school teachers were not confident about teaching science and employing specialist science teachers in primary and intermediate schools might help.
"Where I teach we have specialist teachers in science and the level we can get them [students] to is quite impressive just because we have people who are passionate about the subject and who are pushing their children to do their best in it," she said.
Massey University maths teaching specialist, Associate Professor Jodie Hunter, said the results showed New Zealand needed to spend more money showing primary school teachers how to teach maths well.
She said the TIMSS testing was conducted in 2018 and 2019, providing clear evidence the previous government's national standards in reading, writing and maths, which were dropped in 2018, did not work because the standards were too narrow.
"Unfortunately what happened is in some ways it was too specific because what happened was people taught to the standards," she said.
She said the other culprit was teaching children maths in groups according to their ability, something New Zealand did a lot more than other countries.
"That has an ongoing snowball effect in terms of their achievement because as soon as we start labelling children as low-ability in mathematics then we start teaching them differently I think than those who are labelled as high ability," he said.
Principals Federation president Perry Rush said the results were disappointing but not surprising.
He said a big problem was there was no longer a national school advisory service that ensured teachers knew the best ways to teach maths and science.
"It's not acceptable for there to be individual schools applying different ways of approaching teaching and learning in the absence of any national, coordinated professional leadership around the appropriate approaches that will make a difference. That's missing and it's important that we have that," he said.
Rush said the national standards had narrowed schools' curriculum, which harmed the TIMSS science results but also the maths results because they focused too much on number skills at the expense of other areas of maths.
He said an approach to maths teaching known as the Numeracy Project was also a potential problem. It was introduced nearly 20 years ago and needed to be reviewed because many schools did not believe it was fit for purpose.
Associate Minister of Education Jan Tinetti said New Zealand was seeing longer-term decline in reading, maths and science across most international studies.
"Evidence-based system-wide change is required - that is what the Education Portfolio Work Programme, which covers all learners from early childhood through to the workforce, is addressing," she said.
"We have spent the past three years listening to teaching experts and the community, and are now reframing the curriculum to be clearer about the learning that can't be left to chance - language, literacy and numeracy."
National Party education spokesperson Paul Goldsmith said he would like to see any evidence that the standards had contributed to the TIMSS results.
"I'm sure there'll be lots of reasons given, but what we need to do as a country is address our falling levels of achievement," he said.
"It's a long-standing issue but it has continued to get worse, even in the couple of years since changes have been made."
Goldsmith said an obvious place to start would be addressing truancy because too few students, about 57 percent, were attending school regularly.
He said the national standards were an attempt to better track children's progress and improve accountability and the TIMSS results showed that still needed attention.
Associate professor Maurice Cheng, a science education specialist at the University of Waikato, has worked closely on TIMSS in Hong Kong.
He said it was notable that New Zealand now had no significant gender difference in science achievement, though there had been a difference in favour of boys at Year 9 in 2011.
Cheng said the percentage of Year 5 students who liked science was similar to the international average, but the percentage at Year 8 was a lot lower.
He said students who liked science scored higher than those who did not.