The Government is considering only offering water, low-fat milk or plant-based milk in schools to reduce the sugar intake of young students.
The proposed law change, laid out in a consultation document published on Thursday, aims to reverse research showing that dental decay is now the most common disease reported among children in New Zealand.
Students could be offered plain water, reduced or low-fat milk, as well as unsweetened reduced or low-fat plant-based milks - including soy, rice, almond and oat - with added calcium and vitamin B12.
Education Minister Chris Hipkins said rates of obesity among children increased significantly between September 2020 and August 2021, reflected by the fact that sugar-sweetened beverages account for more than a quarter of children's sugar intake in New Zealand.
"The Government wants to ask what people think about all primary schools offering only healthy drinks, these being water, milk and non-dairy milk alternatives, to their students," Hipkins said.
"Promoting healthy food and drink in schools is common practice in other OECD countries. Evidence also shows the earlier in a child's development that healthy habits can be encouraged, the better."
The rules would not apply to parents of students in that school, who could still choose to provide unhealthy drinks to their children to take to school.
However, schools could go further than the regulations by putting in place a school policy to stop children from bringing unhealthy drinks to school, so long as they consult with their school community and parents can access a written version of the policy on request.
There would be some exemptions to the rules, such as school events to mark religious or cultural occasions such as a powhiri, or drinks consumed as part of the curriculum, for example using fruit to make a drink in a cooking class.
Other exemptions could cover prescribed dietary requirements or where there is a boil water notice in the community.
According to a 2016 University of Auckland survey, of the 819 schools swamped, 67.5 percent of primary and 23.3 percent of secondary schools with a food service offered only milk and water as a beverage option.
The Government is not applying similar rules to food, as the consultation document explains.
"Regulating the provision of healthy drinks is simpler to implement and makes a difference to schools and students. This is because water is the healthiest drink humans can consume. No other drinks are as good at hydrating your body while also being good for your oral health.
"The same cannot be said for food. Fruit is good for you, but only eating fruit is not. A healthy diet requires a balance of different food types."
Auckland University of Technology's public health professor Grant Schofield told AM he does not think banning sugary drinks in schools will make much of a difference to children's health.
"I think you're hardly going to find a school if at all that still sells you a coke to your child when they are in school but I guess the category also includes things like juices, which have just as much sugar as coke," he said.
"I think it would probably be about half our schools, the rest of them have been down this track for a very long time."
ACT MP Chris Baillie described the Government as "control freaks" over the proposal.
"The proposed ban on fizzy drinks in schools is the worst kind of nanny statism from a Labour Government that only knows how to ban and tax stuff it doesn't like,' Ballie, education spokesperson, said on Thursday.
"ACT believes it should be up to schools to decide what to offer students. We don't need control-freak politicians and bureaucrats lecturing children on what they can or can't consume."
The consultation, run by the Ministry of Education, is open for eight weeks until June 2.