Schools that are not in the government's donation scheme are worried it will hurt their ability to collect tens of millions of dollars in voluntary payments from families.
They say the scheme has raised parents' awareness that payments for field trips and camps are optional, and some are confused about what they can be charged for.
More than 1500 schools have signed up to the programme, which pays schools in deciles 1 to 7 $150 per child if they don't ask for donations or for contributions to class trips.
The principal of decile 7 Northern Southland College in Lumsden, Mike Newell, said the school did not join the donation scheme because $150 per student would not cover the cost of the many field trips it runs.
But Newell said he and other Southland principals were worried parents would be less likely to pay for such trips because they were more aware that payment was optional.
"You set your budget and, potentially, if all of a sudden payments don't come in, there's a real risk of schools being in financial trouble," he said.
Newell said the school collected about $400-500 per student in donations and contributions for trips and he was not confident it would get as much this year.
"It's a wait and see," he said.
"We run a tight budget as it is. This year we've already budgeted at a small loss and we're hoping we can pick it up in other areas."
At Waimea College in Nelson, the principal, Scott Haines, said the donation scheme was profoundly affecting the decile 8 school even though it was not eligible for the scheme.
He said some parents were challenging the school's request for a donation.
"In our own setting where we're not eligible for that resource, parents are asking why we're asking because they had understood that actually schools aren't supposed to be asking for donations anymore," he said.
"It's only February, but we're already seeing less school donations coming into the school as a result of this."
Haines said about 60 percent of the schools' families paid the donation each year and he hoped that figure would not fall.
"We were concerned about that from the outset. Certainly, it would appear that our concern has been valid."
While some schools might be seeing a downturn in donations, there were early signs others would continue to get the payments even though they were in the scheme.
The principal of decile 6 Edendale School in Auckland, Jonathan Ramsay, said it was in the government's programme and therefore had not asked for a donation this year.
But about 30 or 40 families had paid a donation anyway, he said.
"At the moment I'm unaware of whether they've paid because they just do it every year and are unaware they don't have to. We are following up with parents who have paid just to make sure they know that they didn't have to."
Ramsay said about four of the families emailed to say they were aware of the government's scheme but wanted to help the school because they knew that opting in had cost it thousands of dollars.