Budget documents show the government was told of "profound" wellbeing benefits from the free school lunch scheme months before it decided to trim its funding.
The findings come from a yet-to-be-published study that also found achievement improved at some schools participating in the Ka Ora, Ka Ako scheme.
The research was supposed to be published in June but was still under wraps.
However, Budget papers published this week referred to the study's early findings.
"Emerging findings support previous evaluation findings, but also highlight further benefits of the programme, including improvements in achievement and the importance of universality," said a December briefing note to Minister of Education Erica Stanford.
"This includes that learners are more settled and able to engage with classroom activity and learning, with some schools showing increased academic achievement resulting from an enhanced learning experience from being more settled and less distracted. Initial findings also indicate that the programme is having a profound impact on the wellbeing of learners," it said.
The briefing said feedback from schools highlighted the importance of a universal lunch scheme that provided food to all children in a given school.
"Feedback from schools, teachers, and learners was that student-level targeting ('means-testing') requires learners to self-identify as in-need, which generates a stigma, shame, and whakamā so significant that they will, in almost every situation, refuse to engage with free kai programmes," it said.
The briefing said earlier evaluations found the scheme resulted in happier, healthier children.
The documents said the lunch scheme reached about 235,000 children - about 27 percent of all school students - but covered 60 percent of children living in material hardship and 67 percent of those in severe material hardship.
Earlier this year, the government cut annual funding for the scheme by $107 million, reducing the per-student spend for children at intermediate and secondary schools to $3.
A March briefing paper about changing the model for Ka Ora, Ka Ako said it was not clear whether lunches could be provided at that price.
"The most significant risk from the proposal is that we have not market-tested or otherwise analysed the proposed $3 per head price. We do not know whether sufficient supply exists to offer lunches to the specified standard at this price across the full range of schools," the document said.
It said the change was also likely to create more work for school staff.
"Schools moving to the alternative model will move from having supported lunch supply (e.g., external suppliers or paid school staff) to managing the ordering, storage, heating, distribution, pack up, and management of surplus of the alternative food option themselves without additional resources," it said.