Twelve schools were providing breakfast, sandwiches or cooked lunches for about 200 children who were turning up to lessons hungry.
Researcher Sherry Carne said the results proved that changes to social policy were needed to counter the detrimental effects food poverty was having on children's health and education in Whangarei.
One local organisation working to tackle the problem of hungry children is Whangarei Kai for Kids.
Founder Ann-Maree White has delivered some 500 lunch packs to low-decile Whangarei primary and intermediate schools since launching the donation scheme via Facebook in April - sometimes up to 30 a week.
Ann-Maree said ideally she would like to see hot lunches back in schools.
"That's the time of the day kids really need that energy, and for some it's possibly the only hot meal they'll get."
She would like to be able to make and serve hot soup to schoolchildren at lunchtime, and is currently sorting through ways of doing that - but red tape could get in her way.
"You need to be health and safety approved (to do that), and I'm not registered and I don't want to be.
"I just want to do what I can to get the food into schools."
She is also looking at providing cans of baked beans and spaghetti to schools that may be able to offer students access to a microwave.
Ms White said empty bellies did not just affect the child in question, but others in the classroom who were trying to learn alongside an irritable, hungry classmate.
This week, Labour announced it would roll out a national food programme to all 650 decile one to three primary and intermediate schools in the country if elected in 2014.