The charity has delivered 42 percent more food to schools and early childhood centres this term than it did in term two.
KidsCan chief executive Julie Chapman said in a media statement that the impact of Covid-19 had been hard for the working poor.
"Some families have lost their homes as they can't keep up with rent. Some are spending days without power in cold rentals as they can't afford to top up the meter. They're sacrificing food. It means more children are coming to school hungry and cold, and that's deeply concerning," Chapman said in the statement.
Chapman said support at school was becoming more crucial. "It may be the only hot meal children get a day."
KidsCan was also sending out thousands of fleece-lined jackets and solid shoes.
"No child should be sitting in class feeling hungry or cold," Chapman said.
"We need to do all we can to support vulnerable families through this crisis. It’s incredibly stressful when you cannot provide enough for your children," Chapman says.
Christchurch teacher Rebekah, who did not want her last name used, said the term "hangry" was relevant for a lot of children at her school.
"They can't function at all if they're hungry. Hunger is a huge element in behavioural issues in the classroom," she said.