A dozen school and early childhood sector groups have united to ask Prime Minister Christopher Luxon to retain funding for the free school lunch scheme, Ka Ora Ka Ako.

In a letter to Luxon published on Tuesday afternoon, the organisations said the programme was critical.

The letter's signatories covered Catholic, area, intermediate and Montessori schools, primary, secondary and Māori principals, both teacher unions, kindergartens and one of the main early childhood education associations.

"As leaders of the education sector, we jointly urge you to continue the government's current level of investment in Ka ora Ka Ako, the school lunches programme," they says.

"One in five children in our country live with food poverty. Nutritious food is essential for learning, which is why the school lunch programme was created. It currently offers lunches to 230,000 students in about 1000 of the least advantaged schools, providing a major safety net against food poverty and poor nutrition."

The letter says research from the PISA (Program for International Student Achievement) study showed students who missed meals due to lack of money are two to four years behind in their learning compared to those who never missed meals.

"Of concern is that the most recent PISA results found 14 per cent of New Zealand students did not eat at least once a week because of lack of money, compared to 8 per cent of students on average across the OECD," it says.

"Your government is committed to improving student achievement and supporting Kiwi families who are facing significant cost of living pressures.

"The most recent research evaluating the Ka Ora Ka Ako programme reinforces the views of school principals that it has led to students being more focussed on their learning, fewer working to support their families, fewer behavioural problems, improved social bonding and reduced food poverty stigma through all students sharing meals together."

The letter was signed by leaders of the Educational Institute, Secondary Principals Association, Post Primary Teachers' Association, Association of Intermediate and Middle Schools, Principals Federation, School Trustees Association, Te Akatea (Māori Principals Association), Area Schools Association, New Zealand Catholic Education Office, Te Rito Maioha Early Childhood New Zealand, Montessori Aotearoa New Zealand, and the New Zealand Kindergartens Network.

Associate Education Minister David Seymour says he is considering cutting the funding by up to half. Photo: RNZ / Samuel Rillstone.

The letter followed recent comments from Associate Education Minister David Seymour indicating funding for the scheme could be reduced.

Seymour says there's no hard evidence the programme improves children's achievement and attendance and he's considering cutting its funding by up to half.

The scheme introduced by the Labour government in 2019 feeds more than 220,000 students at a cost of about $325 million a year.

Last year, the previous government approved funding for the programme only until the end of this year after Treasury advised that evaluations of Ka Ora Ka Ako showed health benefits, but little educational benefit.

"Evaluations of Ka Ora, Ka Ako to date have found strong outcomes for improving nutrient intake, particularly for those 7.3 percent of ākonga with least access to sufficient food at home. The programme generally contributes to happier and healthier ākonga overall," says Treasury's advice.

"However, the evaluations have found no impact on attendance, and ākonga Māori, who make up around 48 percent of students receiving the programme, have not benefited on most metrics, such as school functioning (e.g., paying attention in class), health, and mental wellbeing (with mental wellbeing worse off for those in the programme)," it says.

Health Coalition Aotearoa has defended the scheme, noting that assessment of the programme happened in 2021 when student attendance reached all-time lows due to high levels of covid and other illnesses in the community.

-RNZ.