A teachers' union says the Government should pay the bill for police to vet school staff and helpers.
Until now, any adults working with kids in New Zealand schools and early childhood centres have been vetted by police, free of charge.
But from July, police will enforce a $10 fee for each vetting, and schools and early childhood centres are expected to pick up the bill.
Schools and early childhood centres are already struggling under frozen budgets, NZEI past president Louise Green says.
"Schools and centres that are really struggling will start to really consider what costs they can crib back on and it is the kids that always miss out.
"Our operating grants are under huge pressure, there's power cost rises, staff wages, ICT costs, there are so many things that keep coming at us," she told The AM Show on Tuesday.
"We're struggling - we're already having to ask parents to donate a lot to our schools and centres - and if we've got more costs coming on to us something has to give and it's always kids that suffer."
Not only permanent staff but contractors working on school property and parents volunteering on school events also have to be vetted.
Ms Green says there the new cost might mean vetting could be done less.
"This is one assurance our parents do like. They like to know that those who are going to accompany children on trips, where there's some unsupervised access, that there's some safety measures."
Howick Primary principal Leyette Callister says schools simply can't afford the fee and there should be no question about it being done for free, given that the safety of students is paramount.
Ms Callister says by the time she checks contractors, new staff and any parent help she'll be facing a hefty bill.
"Suddenly my budget that might've been looking okay has got a minimum chunk of $500 chopped out of it."
The Policing (Cost Recovery) Amendment Act 2016 was passed by Parliament in November. It will allow police to charge $8.50 plus GST per vetting request.
Police expect to spend $3.7 million in the 2016/17 financial year to cover staff, infrastructure, banking and training for the service.
There are exemptions from the charges for charities, or organisations that apply for fewer than 20 per year.
There is also a waiver if an agency is facing extreme financial hardship, or in the case of extreme circumstances such as natural disasters or national security emergencies.
However a Cabinet paper on the changes outlines these waivers will be at the Police Commissioner's discretion and police expect them to be needed "relatively rarely".
The Cabinet paper says some of the vetting will still be covered by police - therefore government-funded - for things such as police recruitment and national security purposes, including the British and Irish Lions rugby tour.
The number of checks needing police funding was forecast to be 28,268 in 2016/17.