International testing indicated New Zealand had more bad readers among its 10-year-olds than other developed nations, but the picture improved for teenagers.
The 2020/21 Progress in International Reading Literacy Study (PIRLS) found 29 percent of New Zealand Year 5 pupils failed to meet its intermediate benchmark for reading proficiency, a group which included the 10 percent who did not even meet the lowest benchmark for reading proficiency.
Internationally, 25 percent of participating pupils fell short of the intermediate benchmark and just 6 percent were below the low benchmark.
However, another testing system found older students performed better when compared to their peers around the world.
The 2022 Programme for International Student Assessment (PISA) test found 21 percent of New Zealand 15-year-olds were reading at the lowest level - meaning they struggled with all but the simplest reading tasks measured by the test.
"The proportion of Aotearoa New Zealand students who performed below Level 2 was 21 percent, which was less than the OECD average of 26 percent. The proportion of low achievers in Aotearoa New Zealand was similar to that of Australia and the US - countries that had similar average reading performance," the report said.
It said the percentage of New Zealand students reading at the highest level, level 5, was relatively high.
"In reading, Aotearoa New Zealand had 13 percent of students performing at or above Level 5 compared to the OECD average of 7 percent. The proportion of top performers was similar to that of Australia (12 percent) and the US (14 percent), but this proportion was also better or similar to Estonia (11 percent), Japan (12 percent) and Ireland (10 percent), countries with average scores significantly above Aotearoa New Zealand."