A report behind Treasury advice that said school breakfast programmes did not work, says the programmes may need to be used more, to get better results.
The Treasury cited an Auckland University study done in 2010 which showed that children's participation in breakfast programmes did not result in higher school attendance or achievement.
But the study also showed there was a significant decrease in children's hunger and that more frequent attendance of the programmes may be required to influence attendance and achievement.
Treasury document did not include these findings in its report to the Government.
Treasury doubts on food in schools
Treasury advised the Government it had doubts that the food in schools programme would do anything to improve children's learning.
In the report to the Government early last year, it said there were a range of reasons - not just lack of money - why children might turn up to school hungry.
In the February 2013 paper, obtained by Radio New Zealand under the Official Information Act, the Treasury responded to a recommendation from the Children's Commissioner's Expert Advisory Group to introduce a food in schools programme.
It argued providing food for children in schools was unlikely to be effective.
"Evaluations of school food programmes do not indicate that food in schools programmes are necessarily effective at achieving their intended outcomes.
"For example, a 2012 Auckland University study found a New Zealand breakfast programme had no statistically significant effect on attendance and no effect on academic achievement or student conduct," the Treasury said.
"These findings on academic achievement and student conduct are consistent with the findings of well-designed international studies on school breakfasts in first world countries. Internationally the majority of students found that even where breakfast was offered at school, there was no increase in the probability of a child actually eating breakfast."
It said low income was not the only reason children went to school hungry; other reasons included disorganised parents, children refusing to eat and different cultural attitudes to eating.
Labour Party children's spokesperson Jacinda Ardern said she was surprised by the Treasury's analysis.
"Treasury... needs to actually just keep it very, very simple. Are there children or young people going into our schools without having enough to eat and is there, in part, poverty a reason why that may be happening? Now I think it would be very hard to argue against that," Ms Ardern says.
While pessimistic about food in schools programmes, the Treasury advised the Government if it wanted to do anything immediately it should consider contributing money to an existing food in schools scheme.
That appears to have been behind the Government's decision in May last year to increase its support for the KickStart programme run by Fonterra and Sanitarium.
The Government opposes the idea of a paying for a comprehensive programme, although Prime Minister John Key says the KickStart programme is helping.
"The advice that we've had is that if you look at the youngsters taking up breakfasts in schools, which is obviously part of the Government's programme, there is definitely a group that are willingly participating in that and that's, you know, sitting at around about I think 15 percent of children that broadly that go to decile one, two and three schools," he said.
"As you move out the decile ratings it is less appealing to children because there's, you know, lower levels of deprivation."
Ms Ardern said food in schools would not solve poverty and more needed to be done for hungry children.
"If food in schools is one way we can make a dent in that issue it is just common sense. We can continue to have an ideological argument about how to resolve the core issue around poverty. But in the meantime, there are kids that are hungry and that is one simple thing we can do to alleviate that while we go back to the basics to say how can we fix the problem in the first place and that ultimately is lack of income for families," she said.
The Treasury, meanwhile, conceded in its 2012 paper to ministers that more information was needed to determine how many children were going to school hungry.
Its analysis is based on 2007 information and does not include the effects of the global recession and it says the problem could be much worse.