School uniforms are compulsory in most high schools in Northland and can be expensive.
Noelene Martin, deputy principal of Whangarei Girls' High School, said there was strong interest in the second-hand uniform trading post advertised on the Parent Teacher Association website.
Every family that enrols receives an enrolment pack that includes details of the second-hand uniform sales.
Ms Martin said stationery lists are cheaper now than they were 10 or 15 years ago, however she still hears of kids in classes without any books to work in.
"I go out and I spend $30 or $40 of my own money and have a stationery cupboard that I can dish out if a teacher comes to me and says someone doesn't have any books and I quite often do."
Whangarei Child Poverty Action Group spokeswoman Sherry Carne said back-to-school costs has been raised as one reason people can't afford food and turn to services such as food banks.
"It has definitely been raised as a cause of empty food baskets. It's not just uniforms but everything else that goes with it. This time of year stretches already tight budgets."
Owner of Northland School Wear Kaye Jordan suggests that parents of children who need to be in a new uniform next year start thinking of that cost now, so they have a year to save for it.
Both Bethells Uniforms and Northland School Wear offer a layby system, where families can put aside money all year round for uniforms, as a way of budgeting for the expense.
Keshia Nicolson of Bethells Uniforms said the uniform was an investment.
"It may be $200 or $300 on the day, but we outfit the kids with the intention of getting two years wear out of the uniform. Which, if you add up the cost of having the kid in mufti clothes, would probably work out good value."