Ministry of Social Development figures showed that 36,000 families needed help getting their children to school last year. The ministry paid out $6.5 million in benefits for school expenses - $5.28 million of this for uniforms.
The Uniform Shoppe in South Auckland has been supplying Manurewa High School uniforms for 50 years, but general manager Janet Igrisan believes she lost the right to retail its clothing because she refused to pay a financial incentive.
Last year, the school put the right to retail its uniform up for tender, and its tender application document asked suppliers for "details of any school incentive options available".
Manurewa High principal Salvatore Gargiulo sternly denied that incentives had influenced the choice of a new retailer.
He said that the new supplier, Canterbury, provided better-quality uniforms at a cheaper rate for parents.
Asked whether Canterbury offered any incentives, he said the brand had provided a sponsorship programme for disadvantaged children at the college.
Other Auckland-based uniform suppliers confirmed that secondary schools were increasingly seeking incentives - in cash, scholarships or sports equipment - for the right to retail their uniform.
School Uniform Centre managing director David Kranz said incentives were not always solicited, and some suppliers actively offered financial rewards to schools to secure contracts.
He said that he had felt "frozen out" of one school uniform deal because he did not believe in paying a financial incentive.
"Schools go towards those that can sponsor their rugby team. But there's no free ride - someone pays for it somewhere down the line," Mr Kranz said.
Principals Federation president Paul Drummond said he did not believe it was common for schools to seek bonuses from suppliers.
He said schools were motivated by the same commercial realities as any business. But he emphasised that they had to be careful that their commercial aspirations did not penalise families.
"It is not uncommon for schools to have exclusive suppliers," Mr Drummond said.
"But it is certainly important that schools strike the balance between doing something that is of financial benefit to schools but at the same time not passing that extra cost on to parents."