A report from the OECD's Programme for International Student Assessment (PISA) shows New Zealand's 15-year-olds spend more time on the internet than their peers in all countries except Denmark, Sweden and Chile.
It says results from the 2018 PISA tests show New Zealand teens were spending 42 hours per week online, well above the OECD average of 35 hours per week and 22 hours higher than in 2012 - equal with Costa Rica for the biggest increase of any of the 79 nations and economies in the study.
The report also found New Zealand was one of just five countries where use of digital devices at school was associated with better performance in reading.
The PISA tests have shown a slow decline in New Zealand 15-year-olds' achievement in reading, science and maths during the past 18 years.
An education professor at the University of Auckland and chief scientific adviser to the Ministry of Education, Professor Stuart McNaughton said there was not enough evidence to show increased screen time was to blame for falling achievement in the PISA tests and other measures.
"It's a bit of a long bow at the moment. We can't link causally, easily, the increase in device use and use of the internet and the dropping reading achievement scores but it is certainly possible that there is a relationship," he said.
McNaughton said it was clear that, apart from extreme high use, the amount of time spent online was not as important as what young people were doing while online.
"The issue around the relationship or potential relationship with achievement over years is whether or not the digital device usage, internet, social media, is somehow in conflict with or undermining our reading and writing activities, school-related or non-school-related," he said.
McNaughton said the report showed that reading longer texts was associated with better reading scores, and the challenge was to find ways of ensuring young people were reading them.
The report said the time teachers spent using digital devices in class had a negative impact on students' reading performance in most countries, but New Zealand was one of five that bucked that trend.
"The association between time spent using digital devices and positive performance is only positive in Australia, Denmark, Korea, New Zealand, and the United States," the report said.
It said New Zealand 15-year-olds were using digital devices in class for about 84 minutes per week - less than Denmark, but more than the other three nations - and the associated increase in reading scores was higher than in the other countries.
It said browsing the internet for school work was the digital activity most strongly related to reading performance and New Zealand was among countries where half or more of students did that every day or almost every day.
Some activities, especially playing simulations, had a negative impact on students' reading performance.
The principal of Albany Senior High School, Claire Amos, said she suspected New Zealand's good performance was the result of deliberate efforts to find good ways to use technology to support literacy.
"We have very proactively looked at how we can use these technologies to enhance literacy teaching and learning and I think we've front-footed that," she said.
Amos said she was not surprised that New Zealand teens were spending more time online than their peers in most other countries because schools had encouraged students to use their devices and there was high internet coverage across New Zealand homes.
But she said she was concerned that the report showed a strong digital divide.
"We still have a tail end of young people who aren't doing as well in lower socio-economic areas," she said.
"That just doubles down on the need for us to really get on and close that digital divide in our schools because, where are young people have access to technology, where our teachers are confident in using that technology, it's clearly having a positive impact on their literacy learning and their literacy acquisition and skills."
The study found that, internationally, teenagers who read printed books were better readers than those who read digital books or no books at all.
It also found that teens at schools that expected them to read texts longer than 100 pages were better readers. New Zealand had the 12th highest proportion of students at such schools.
The report said, across the OECD, 54 percent of students said they were taught at school how to recognise if information was biased.
New Zealand's teens scored well on questions testing their ability to discern opinion from fact, and were good at navigating the internet to find information from multiple sources.
It said 90 percent of New Zealand students had access to a computer they could use for schoolwork and a link to the internet at home, though the figure ranged from about 80 percent at lower-decile schools to more than 95 percent at higher-decile.
It said enjoyment of reading had fallen in New Zealand and in many other countries and enjoyment was closely linked to high performance in reading. New Zealand teens were reading for enjoyment for about 3.5 hours a week, slightly less than in 2009, but the same as in 2000 and the same as the OECD average.
The report found, internationally and in New Zealand, that when students were reading online, fewer were spending much time reading emails than in 2009, but more were reading online chats (about 90 percent, up from less than 60 percent in 2009), reading online news, searching for information on a particular topic, participating in online discussion groups, and searching for practical information.