Some schools are facing criticism for charging parents for more than they are legally obliged to pay.
Education Review Office (ERO) inspectors have discovered 24 schools, ranging from primary to secondary, have asked for the extra payments over the last 20 months, the Sunday Star Times reported.
Inspectors found:
* Eleven schools called donations "fees" or "term payments", or did not make it clear that donations were voluntary;
* nine schools charged a photocopying or paper fee;
* four were insisting parents pay for their children's access to the curriculum;
* one was charging for internet access and another for overdue library books; and
* three were charging extra for enrolment in digital classrooms, where children work on laptops rather than using pen and paper.
The Ministry of Education said they are unable to stop the schools because, although the law entitles children from age five to 19 a free education, there were no specific rules about what schools could and could not charge for.
However, state-integrated schools must make it clear all donations are voluntary and were not allowed to charge for expenses such as photocopying or internet access.
Schools have defended their stance, by saying they have to raise the extra cash because they do not receive enough in Government funding.
Education Minister Anne Tolley told the paper only a small number of schools were charging inappropriately.
"It's not a question of punishing...We need to be able to trust these schools won't do it again once their error has been made clear to them.