Education Minister Anne Tolley has told an integrated school in Wairarapa that the way it asks parents to pay donations does not make it clear which are compulsory and which are not.
In 2009, Rathkeale College in Masterton was criticised by parent Karen Bock after the board chairman suggested that she mortgage her house to pay $13,000 in fees.
Ms Tolley says the invoice given to the parents of those at the school, which is partly stated-funded, shows only one figure, which could mislead them into thinking they have to pay the full fee.
In a letter to the school board of trustees, Ms Tolley also raised concern about interest being charged for late payments of voluntary donations.
She wants the school to ovehaul how it charges fees by February.
Rathkeale College principal William Kersten says the school is working with the Ministry of Education.