Parents are skipping meals to pay for school supplies, and siblings are attending school on alternate days because they can afford only one bus pass, a children's charity warns.
Children around the country are heading back to school this week but KidsCan warns many students living in poverty will be missing from classrooms.
Staff at nearly 200 low decile schools and early childcare centres told the charity about the "heartbreaking" situations students are in, with some spending lockdown in overcrowded, subpar houses, without internet or a digital device.
"The anxiety and stress levels are now taking its toll on perseverance and engagement," one principal wrote.
Another teacher said one family had paid for uniforms but had no money left for power or food.
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Some teachers were paying back-to-school costs from their own pockets while many schools were helping with stationery, laundry, uniform grants and transport.
"Experiencing children not having the tools to learn at the beginning of the year is all too common," one wrote. " 'How does it affect attendance?' is not the real question. How does it affect mental wellbeing when you are the odd one out without the tools to learn?
"It's soul-destroying. It makes you want to give up and not go to school."
As well as money struggles, some families are expected to keep kids home for fear of Omicron spreading.
Edmonton Primary School principal Margaret Samson says she is expecting 50-60 per cent of students back when the school in West Auckland opens on Thursday.
She has plans to visit the other families and talk through their concerns, and is hoping to have full attendance within two or three weeks.
"Often people, when they hear about [the safety measures] we have in place, that lowers the anxiety."
Samson said some students were isolating after siblings attended Soundsplash in Hamilton, and she was aware of some teachers having to isolate after exposure to Omicron. Everything was changing by the day, she said.
The school would be making every effort to stay open - after the last lockdown it was clear children needed to be in class, Samson said.
"They need to be with their friends, they need to be socialising. We noticed that the more the children came, the better their emotional state was, and their resilience."
During lockdown, the decile 4 school in Te Atatū South was regularly delivering food packages to 50 families. Most of that food was provided by KidsCan, which sent out more than 6000 emergency food parcels nationwide over the lockdown.
Samson said many of their parcels went to families who had never before needed help, but the parents had lost jobs and were struggling.
"What I'm really proud of is that they did reach out, so we've been able to build that relational trust. So we feel reassured that they will let us know if they're actually needing any help."
This year there is still great need, she said. "My concern is with Omicron that families will be having to isolate for longer."
Many secondary schools are also expecting their rolls to drop as students have taken jobs to keep their families' heads above water, KidsCan found.
James Cook High School principal Grant McMillan said most schools in Auckland would have had some students working full-time last year - more so in South Auckland and schools close to retail and logistics hubs.
It won't be clear until mid-February how many young people would stay away, McMillan said, but he expected the "vast majority" of students to return.
Some who took jobs last year could come back for about six months to complete Year 13.
"I'm expecting that some students will stay in employment but I'm not getting a strong sense that'll be a huge number."
When he started as principal, the Manurewa school had had many students who would not come to school for financial reasons, such as not being able to afford uniforms - but the school had become more proactive about finding solutions to get those kids back in class quickly, McMillan said.
That included letting parents buy generic uniform items from shops such as The Warehouse, and making KidsCan jackets part of the official uniform. The jackets had been one of the most popular items from the charity last year.
While clothing was still in demand, free school lunches and sanitary products were reducing the amount of help James Cook needed from KidsCan to some extent - which meant KidsCan could help other kids in need, he said.
McMillan and his wife donated to Kidscan themselves. "They're an amazing charity ... I"m just so impressed by what they do and how they do it."
KidsCan is now working with a record 854 schools and 122 early childcare centres, but it says there's still more need and new support programmes are being developed this year. See their website, www.kidscan.org.nz, to donate.