Many students will start the school year next week without shoes, an empty tummy and dirty clothes.
Schools say this has been exacerbated by COVID-19 and there are a myriad of challenges faced by children living in poverty.
At Whangarei Primary School, some children arrive at school in oversized shoes or do not even have shoes.
Its learning support co-ordinator Kim Tavinor said she had seen the impacts first hand.
"When it comes to turning up in school, we've got kids in the middle of winter turning up in skinny little clothes, basically T-shirts and shorts, nothing on their feet, no jackets they turn up wet because they walk to school," she said.
"Often they don't have bags because they have nothing to put in them because they don't have any lunch, no breakfast."
This is not a new problem, but Tavinor said it became worse as the lockdowns hit.
"We've got parents that obviously lost their jobs, we've got other parents who, like there might've been two family [members] working and now they're down to one, plus we've had lots of families that were obviously put on the subsidy."
At the other end of the country, Invercargill Middle School principal Sarah Read said even arriving at school became a challenge for some children.
"There were some that struggled to get to school firstly, 'cause they were really worried about COVID and getting it for their kids so they didn't want to send them back. There were others that had lost their jobs so didn't have a lot of income and they were out trying to find work and kids were at home helping look after little people."
New research from Colmar Brunton, commissioned by KidsCan, has found children at decile 1-4 schools, who are the worst off socially and economically, face a big hurdle in getting their basic needs met.
The research found principals were buying togs and towels from second-hand shops so kids could go to swimming lessons.
One intermediate teacher told researchers kids said they had not eaten in days or were getting "pink soup" - the water cheerios were cooked in.
Researchers found some children came to school with sores and bags under their eyes.
Waihi College, on the foot of the Coromandel Peninsula, is suffering from these kinds of problems.
Its principal Alistair Cochrane said the problems were "significantly worse" than previous years.
He said winter was the toughest time, but the start of the year was also challenging.
"Sometimes there's changes in uniform if kids are going from one school to another, you've got your stationery requests, you want to set your kids up and parents want to set their kids up the best the can and we're seeing some kids actually not come back to school when they should be back at school because they're too embarrassed."
Since COVID-19 struck, KidsCan has had a huge increase in children needing its services, the charity's chief executive Julie Chapman said.
It was supporting 40,000 children a day with food items compared to 30,000 in the first term of last year.
"We expect it's going to be one of the toughest years for children and parents as they are trying to get ready to go back to school."
Chapman said food insecurity was so bad, KidsCan's programmes will still be needed in schools even with the expansion of the government's food in school programme, she said, for breakfast and top up foods during the day.
"Now more than ever we are hearing about children who will go home to nothing in the cupboards and therefore they won't eat for another 12 hours so we are looking at what we can do to give those kids something they can take home with them as well.
KidsCan works with 822 schools across New Zealand, predominantly decile 1-4 schools, and supports and childhood centres in areas of high deprivation. As well as food it provides access to shoes, raincoats and health and hygiene items.
School starts from next week, between 1 and 9 February.