Reading and writing levels among poor children remain stubbornly below those from wealthy backgrounds, with some education experts now turning to health researchers for help to "break the cycle".
National Standards results show children from low-decile schools are more than twice as likely to leave primary school with low literacy levels when compared with high-decile pupils - although overall, there are still one in five children arriving at high school without expected reading skills.
Differences in the reading levels between students from high and low-income families narrow slightly as the children grow older, but data shows the gap in writing ability actually worsens by the time students head to high school.
"You have the children that come into school with lots of literacy knowledge, enough to attach new knowledge to, so they will learn to read no matter how they are taught," said Massey University's Dr Alison Arrow.
"Whereas kids that come in with limited knowledge have nothing to build on. They don't know spoken words have sounds in them, for example.
"So if they don't get explicit instruction when they get to school they struggle to catch up and they will lag behind for the rest of their school career."
The trend in reading and writing data is a problem New Zealand has been aware of for at least a decade. OECD studies show we have one of the widest gaps between rich and poor when it comes to reading, and it hasn't changed over time.
While there has been increased talk about raising achievement for "priority learners", Education Review Office reports show that hasn't necessarily been do-able in practice.
For example, ERO found only a quarter of schools had practices to catch up "priority learners" that were highly effective; that few schools effectively identified and targeted the full range of students at risk of failing; that 30 per cent of teachers in Year 1 and 2 classrooms had "little or no sense" of how critical it was for children to develop confidence and independence in early reading and writing; and had "minimal understanding" of effective reading and writing teaching.
Some critics believe the issue is linked to the way New Zealand stages reading intervention. It has recently funded two studies aimed at helping teachers to more effectively "catch up" disadvantaged kids in their first year.
Dr Arrow is currently working on The Early Literacy Project, a $1.25 million intervention which aims to increase the knowledge of teachers working with new entrants.
The programme differs to regular intervention in that it is based on phonics (learning sounds), and begins within six months of the child starting school. New Zealand's traditional intervention, Reading Recovery, is whole-language based (reading books) and children wait until they are 6 years old to take part.
Dr Arrow said current support for phonics, or "decoding", was patchy and could be used more effectively in Year 1. "What we'd like to see is something that's a bit more systematic and supported in terms of intervention that really targets children that are starting to struggle within the first six months," she said.
"We know if children aren't developing decoding skills in that time that's an indicator that they're going to have quite specific difficulties."
The second study is a 10-year research project called "A Better Start", a joint education and health exercise costing $34 million.
It will take at-risk Christchurch students and work with families to address health issues such as hearing defects or housing-related problems like bronchitis, and then also employ a phonics-based literacy intervention, but with an added focus on vocabulary.
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Professor Gail Gillon, the project's co-director, said it was a "steep change" in the way interventions worked.
"We're not just saying it's the teachers' problem. Healthy wellbeing is critical to learning.
We need to address this significant issue in a holistic way."
Both Labour and the Green Party said while quality teaching made a difference, underlying inequality issues also had to be addressed.
"Lifting families out of the poverty trap, providing second-chance learning opportunities for parents, and tackling issues like housing quality and affordability are all part of the answer," Labour's Chris Hipkins said.
Education Minister Hekia Parata said the Government had lifted benefits, and supported breakfast-in-schools programmes in recognition of the effect socio-economic factors could have on learning.
"I do not agree with those who argue that economic disadvantage is an insurmountable barrier to learning. The challenge for us as policy makers is to identify what works, support schools and teachers to provide it and ensure other teachers know about it."
Alternative to reading recovery considered
Deputy principal of Bellevue School and trained reading recovery teacher Pam Seath said reading recovery played an important role in helping students, but said the school was considering alternatives which would help more children.
"I think reading recovery still has a place, it's an excellent programme for picking up children who are below the standard that would be expected."
Mrs Seath said teachers were seeing an increased need for reading recovery.
"I think the thing that is going against it at the moment is that there are more and more children who are probably needing this pick up, who haven't got a lot of language experiences when they come into school."
She said the reading recovery programme was very beneficial to students but programmes with a broader reach were needed.
"It is a great programme, but it is just getting to more children, and that's why we would look at other things," she said.
She said many schools, including Bellevue, were looking at other programmes which could cater to more children. "We're looking at anything that can cater for more children rather than just the individual.
"If you're only catering for three or four children, they might be on the programme for about 20 weeks, so that's a lot of resources and a teacher tied up just for those individual children."
- Anna Whyte