An Auckland school decided to increase parent donations by 25 percent on the same day a proposal to fly 12 teachers to the Cook Islands for a working trip went before its board of trustees.

Documents released to the Herald on Sunday under the Official Information Act show Blockhouse Bay Intermediate's board of trustees approved raising annual donations from $80 to $100 during a meeting on October 19, 2016. The plan for the trip, which cost nearly $19,000, was discussed minutes later.

The school's principal Michael Malins said the two decisions were unrelated.

However, two parents spoken to by the Herald on Sunday criticised the timing of the decisions, and one mother said it was "awfully cheeky".

The Herald on Sunday last week reported the Auditor-General would make inquiries about the Cook Islands trip during its next round of school spending audits.

Blockhouse Bay Intermediate spent $18,976 on 12 teachers' flights and insurances for the two-week trip that aimed to immerse staff in Cook Islands culture and teaching practices to help them better teach Pasifika pupils. Teachers paid for their accommodation and other expenses themselves.

Further inquiries by the Herald on Sunday have revealed the Auditor-General had highlighted the school's spending on another overseas trip during an earlier audit.

In 2016, Blockhouse Bay Intermediate paid $26,000 to send three teachers and 18 pupils to Korea on a cultural exchange. The trip cost $82,000 in total, but students' families funded $52,000.

Ministry of Education guidelines say schools should usually fundraise for overseas travel for students and teachers.

The Auditor-General's 2016 report also said the school paid $2500 for expenses for an overseas trip that year without appropriate receipts.

Malins said the Korea trip was planned before he took office and the issue with the receipts was "not in line with the school's current policies and procedures for financial management".

He added that all student cultural exchanges were now funded by their families.

Regarding the decision by the board of trustees to raise parent donations on the same day as the Cook Islands trip was proposed, Malins said school boards of trustees usually set the next year's budgets during October meetings.

The increase in the cost of donations, effective last year, was the first in several years. The change preceded a "massive investment in learning resources and technology" by the school.

But a mother of a Blockhouse Bay Intermediate pupil claimed the fact donations were put up on the same day the Cook Islands trip was proposed to the board seemed an unusual coincidence.

"They're two big decisions in the same meeting that probably wouldn't usually occur. I don't think you'd want to announce that you're spending that sort of money for the staff to go away but also say to parents 'you're going to be hit in the pocket if you choose to pay your donation'."

Another parent, who had worked as an accountant, also questioned the board of trustees' decision to raise donations and then spend thousands of dollars on an overseas trip.

"I think that is awfully cheeky, especially at a time when a lot of families are struggling," she said.

"One of the reasons I don't pay my donation anymore is because I'm unhappy with spending like that.

"Something needs to change, in my opinion, with the spending of school money."

The funds put towards the Korea and Cook Islands trips could have been better spent on supporting struggling learners, she said.

New Zealand Parent Teacher Association president Diane O'Sullivan claimed the board's decision to raise donations was unfair given the context.

"I think it was a foolish thing to do, not a good idea. If I was a parent there and I heard about that and my request for donation went up 25 percent, I might be a little hesitant in paying that."

However, O'Sullivan acknowledged boards of trustees were independent and had authority to decide how to spend schools' money.

Ministry of Education learning support national director David Wales said although school boards of trustees could ask for donations it was a parent's choice whether or not to pay them.

School boards were accountable for all aspects of the school's performance, including decisions on financial expenditure.

"If a parent has questions with how a school is spending money they should speak to the board of trustees," he said.

"If they feel the response is unsatisfactory they should contact our local office."

Wales said the ministry first learned of Blockhouse Bay Intermediate's spending on the trip to Korea after the Auditor-General's 2016 audit, but would not be drawn on whether the ministry considered it appropriate.