Poverty, household stress, busy parents and digital dependence are among the complex factors blamed for a rise in the number of children starting school with a toddler's vocabulary.
Photo: 123rf
Education specialists say more schools need to shift their focus to getting kids talking to turn around declining literacy rates - and the gaps for Māori, Pasifika and children from poorer families.
At Wellington's Holy Cross School there are just over 200 children on the roll, with 28 different ethnicities.
The school's principal, Celeste Hastings, said for many, English is their second - or even their third or fourth - language.
While exploring ways to boost spoken language for all students, she came across Auckland University's Intensive Oral Language programme, they've dubbed "Think Talk Create".
"It's a programme and support that works for every student, so they have English as their first language or not, and that I think is what makes it so appealing, because every child in the class benefits."
Deputy principal Susie Sumner explains it's a topic-based approach, where children are "gifted" words to do with a specialist subject during intensive sessions and then taught to use them in creative ways.
Dr Jannie van Hees, who designed the programme, said it aims to mirror the ideal conditions for learning in the very early years.
Every baby is born with incredible potential to learn - and language is the key to unlocking that potential.
"Language is the stimulus to open up the neural pathways in the brain."
Dr van Hees said children from non-English speaking homes often started school with few English words, but they quickly caught up because they knew how to have a conversation.
It's the children who have been starved of any language who are really disadvantaged.
A Canterbury University study found 61.5 percent of new entrants in some low-decile schools in Christchurch struggled to express themselves in words.
But van Hees said it's never too late.
"You say 'OK, it's never too late. Your brain is good, it just needs to get the right opportunities and environment and you can learn."
Van Hees said once families realised how important it was to talk to their children, they're totally motivated to do it.
"But I also think we need a big review of the way we have pedagogy in the classroom - is it conducive to growing the full potential of our kids or not, and I think generally it isn't."
Van Hees said with New Zealand's literacy, maths and science levels declining for 20 years, it was time to do things differently.
Further south, another project has been attracting international attention for its impressive results in accelerating reading, spelling and oral language among new entrants at low-decile schools in Christchurch.
Professor Gail Gillon from the Child Wellbeing Research Institute is leading the Better Start Literacy Approach, which helps children differentiate between different sounds in words and boost their vocabulary through quality story books and culturally relevant activities.
"Even though these tamariki are coming in with lower levels of oral language skills, through the Better Start Literacy Approach we're seeing we can really accelerate that really quickly and the teachers have been doing an amazing job of really developing those foundational skills within just 10 weeks of classroom teaching."
The programme is now being rolled out to other communities in Christchurch and Auckland.
The institute has also developed an assessment tool for preschoolers to pick up problems even earlier.
Screen-time cops a lot of the blame for children's poor language skills - so it's ironic these researchers are harnessing kids' fascination with screens to gauge gaps in their language, through a fun online game.
Professor Gillon said it's a huge improvement on the old paper-based assessments, which involved teachers having to make a referral if they suspected a problem.
The group has recently received $100,000 from the Canterbury Medical Research Foundation to trial the tool, working with 50 four-year-olds with speech-language impairment and those at risk for dyslexia or learning difficulties.