One in four New Zealand children is thought to be living below the poverty line. The free food recommendation was part of the expert group's Solutions to Child Poverty paper, released last week.
Children's Commissioner Dr Russell Wills, who formed the expert group in March, said several schools already had similar programmes in place.
"The principals are doing that because they know kids are coming to school hungry, and hungry kids don't learn.
"Some do it out of their own budget, and some do it in partnership with NGO's like Kids Can," he said. "The kids don't just learn better, they relate to each other better, the behaviour in the class settles down and the whole environment improves."
Schools providing meals had also adjusted programmes to suit their individual communities, Dr Wills said.
"Each school will do it differently - some will have a meal laid out in the school hall. Others will have a basket of healthy food choices in the classroom, that kids can just help themselves to when they want to.
"They've also learned some tricks in terms of how you feed kids without stigmatising those kids and creating dependency."
Mr Wills said it was important people understood programmes offering food to low-decile students aimed to assist children and families living in poverty.
"There are parents who are poor and who manage their money well, who still sometimes can't afford to feed their children.
"This is one of those times when you have to put the needs of children ahead of other considerations."
Though the expert group's report was released last week, Dr Wills said his office was yet to hear from the Government about the recommendation.
By the numbers
Children living in poverty are deprived of the material resources and income required for them to develop and thrive.
270,000 kids, or 25 per cent of New Zealand children, live in poverty (2011 figure).
35 per cent of children living in poverty are from families where only one parent works.
Poverty rates for Maori and Pasifika children are consistently higher than Pakeha children - typically double on most measures.