Surprising declines in the academic performance of girls, Asian students, and pupils from high socio-economic backgrounds have been revealed in an international report.
The results of the 2015 Programme for International Student Assessment (PISA), which measures how well countries prepare their 15-year-olds educationally to meet real-life challenges, was released tonight.
New Zealand's international ranking increased across science (12), mathematics (21) and reading (10) - up from 18, 23 and 13, respectively.
But this was not reflected in the scores.
Compared to 2012 - the last time a PISA study was undertaken - New Zealand students' scores declined slightly. The biggest drop was in maths, where the average score fell from 500 to 495.
However, all were above the Organisation for Economic Co-operation and Development (OECD) average, and the Government praised the results as "pleasing".
Education Minister Hekia Parata told the Herald she believed the results were "pretty good", and New Zealand had "stabilised and consolidated" its scores from 2012.
However, she conceded: "We've got more work to do, absolutely."
One of those areas was New Zealand's well-documented poor educational equity, again highlighted in this report.
It had improved from 2012, with scores for students from low socio-economic backgrounds improving slightly for science, reading and maths.
The improvement in the correlation between socio-economic status and results showed "we're getting traction" in tackling New Zealand's historically high education inequity, Parata said.
"That speaks to the wider social investment approach that our Government has been taking."
Surprisingly, scores for students from high socio-economic backgrounds decreased across all three subjects.
"Changes in average achievement appear more pronounced for high socio-economic students than for low socio-economic students both in the short term [since 2012] and over the longer term," the report states.
New Zealand has one of the highest proportions of 15-year-olds achieving at the highest proficiency level in science and reading, according to the 2015 PISA report.
One in five New Zealand students (20 per cent) are among the top performers in at least one subject area, compared to the OECD average of 15 per cent; and a relatively high number of students who are top performers in all three areas, at 6 per cent, compared to the average of 4 per cent.
However, long term trends across all subjects show a decline in the number of students at the higher levels, and an increase at the lower levels.
Following a dramatic fall in overall results between 2009 and 2012, achievement levels have stabilised somewhat in 2015, but still show a slight decline.
The average score in maths dropped from 500 in 2012 to 495 in 2015, science dipped slightly from 516 to 513, and reading also saw a dip from 512 to 509.
Girls saw a sharper decline than boys, with their scores in science dipping from 513 to 511, compared to the boys' dip of 518 to 516.
Reading fell four points compared to the two point drop from the boys, while maths fell by eight points, compared to a one point drop in the boys' scores.
Craig Jones, the Ministry of Education's deputy secretary for evidence, data and knowledge, said: "I think we should be quite proud of where we stand internationally."
However, he admitted there was "plenty more to do", including in maths and closing the gap between those at the bottom and those at the top.
Louise Green president of the New Zealand Educational Institute (NZEI) said the Government needed to invest more in tackling under achievement in areas of poverty.
"There seems to be a really big gap ... for kids in those low socio-economic areas. That's basically saying to us, stop the rhetoric and actually get the investment into the areas where it's needed and get the resourcing into schools in high poverty areas ... to actually make a difference for these kids," she said.
"And also deal with the poverty issues outside school because the link's really clear, the OECD's made that really clear."
Labour's education spokesman Chris Hipkins said there was "nothing to celebrate" in the report.
"These are bad numbers - our average scores across all three subject areas have declined.
"The numbers speak for themselves," he said, branding National's performance on education "a failure".
Around 500,000 15-year-olds from 72 countries took part in PISA 2015, including 35 OECD countries. More than 4500 New Zealand students,from 183 schools, participated.
The PISA report comes less than a week after the 2015 Trends in Mathematics and Science Study (TIMSS) showed New Zealand school-children are performing below the international average in maths.
BY THE NUMBERS:
• 509 - The average reading score for New Zealand students, higher than the OECD average of 493.
• 513 - The average science score of New Zealand students, compared to the OECD average 493.
• 495 - The average maths score of New Zealand students, above the OECD average of 490.
• 10th - New Zealand's ranking in reading, up from 13th in 2012
• 12th - New Zealand's ranking in science, up from 18th in 2012
• 21st - New Zealand's ranking in maths, up from 23rd in 2012
• 1st - Singapore's ranking in all three subjects
• 5.9% - the proportion of NZ students who sit among the top performers for reading, science and maths, compared to OECD average of 3.7%
KEY NZ FINDINGS OF PISA 2015:
• A more pronounced decline in girls' achievement compared to boys'.
• However, girls continue to outstrip boys when it comes to reading, and New Zealand girls reading skills are also much greater than the overall OECD average .
• Maori achievement is below the OECD average, but has stabilised since 2012, with scores staying essentially the same.
• Pasifika students demonstrated an improvement in scores across science, maths and reading.
• Asian pupils showed a decline in performance, but remained above the OECD average in all three subjects.
• New Zealand's educational equity is still far below other OECD countries, but it has improved since 2012.
• More children from low socio-economic backgrounds are achieving, and saw an increase in scores across all three subjects.
• However, children from high socio-economic backgrounds saw a decline in scores across all three subjects tested.
• New Zealand has a relatively high proportion of students who are top performers in all three subjects (6 per cent) compared to the OECD average (4 per cent).