Every state school that opened before 2015 received infrastructure grants ranging from $50,000 to $400,000 under the programme announced at the Labour Party conference, but 330 state integrated schools, including Kaitaia's Abundant Life School and Pompallier Catholic School, missed out.
And that breached their agreement with the Crown, according to National MP Nikki Kaye.
"Education Minister Chris Hipkins has said state integrated schools can use attendance dues to modernise or upgrade their buildings. Mr Hipkins clearly doesn't understand his own Government's responsibilities," Ms Kaye said.
"Attendance dues are used for the payment down of debt to get the buildings to a state standard. The Crown has accepted the obligation to maintain integrated school premises in a state of repair comparable to a state school's.
"The integrated schools have a clear case that if the Crown sees the need to increase maintenance funding for state schools then the Government has an obligation to provide funding for state integrated schools, otherwise the government is discriminating.
"The minister needs to fix this mistake quickly, otherwise his Government is heading to court, and the minister will have to defend what appears to be a clear breach of the agreement with the Crown."
Ms Kaye said Associate Education Minister Jenny Salesa was reported to have had a "crisis" meeting with integrated schools' representatives last week, and Mr Hipkins should have been there to explain why he had potentially broken the agreement.
"But it's no wonder Mr Hipkins is confused about the agreement, given he's delegated all responsibility for the relationship with the 330 schools to his associate minister and hasn't formally met with the Association of Integrated Schools," she added.
"Mr Hipkins has a habit of rolling out flawed and unfair education policies. The donation scheme excluded a third of schools, the rollout of the learning support co-ordinator roles was deeply unfair, and this school infrastructure announcement may have broken a fundamental agreement with 330 schools representing 90,000 students."
Abundant Life principal Mark Tan said he wasn't losing too much sleep over missing out on the funding, although he would have no trouble spending the approximately $140,000 he would have been entitled to if integrated schools had been included.
"If we get it it will be a bonus," he said. "If he don't we'll just carry on."
The funding, he added, would be four times the school's current annual maintenance budget.
(If Pompallier Catholic School had been eligible for the grant it would have received $104,000).