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 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.
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.
Its the same as the UK austerity playbook that as wrecked the NHS.