Donations to state schools have soared by 30 per cent in the last four years of official data, as schools turn to parents and charitable trusts to fund extras beyond what taxpayers provide.

Parents at the country's most expensive state school, Auckland Grammar, are being asked to fork out a record $1225 this year - up 4.3 per cent from $1175 last year, when consumer prices rose only 1.6 per cent.

Official data provided by the Ministry of Education in response to a Weekend HeraldOfficial Information Act request shows average donations to all state schools rose by 30 per cent from $144 per student in 2012 to $187 in 2016.

That was nine times the 3.3 per cent increase in consumer prices in that period.

However the official data includes donations from charitable trusts as well as parents. For example Sir Edmund Hillary Collegiate Senior School in Ōtara recorded $520 in donations from local pokie trusts in 2016, averaging just over $1 for each of its 496 students.

The collegiate's middle school principal Kallie Ngakuru-Syder said she used the pokie trusts a lot.

"We did a lot of sun shades, big umbrellas and things, our allocation won't allow for that. All our school trips are paid for through trusts - we have been to Rotorua, we are going to Waitangi this year," she said.

But schools are also asking for more from parents. A Weekend Herald survey sent to the country's 2531 schools late last year, which drew 544 responses, has found that requested parental donations have gone up 2 per cent from an average of $109 last year to $111 this year.

Only 21 per cent of schools no longer ask for any donation - although this number has actually increased by a net six this year, as 11 schools in our survey stopped asking for donations and only five started requesting them.

At decile-4 Waitara High School in Taranaki, new principal Daryl Warburton has given up more than $40,000 in revenue by scrapping all fees for learning-related items such as workbooks, technology, school trips and camps, as well as a requested $100 donation.

"The bottom line for me is that we didn't want those sorts of things to get in the way of a quality education," he said.

"Subsequently we have plenty of engagement from our families. When you are calling a parent, you no longer have to chase up those things, you can just focus on the learning."

James Le Marquand at West Auckland's Arohanui Special School has given up $4000 by scrapping a requested $90 donation, and Phil Palfrey at Rotorua's Kaitao Intermediate has stopped asking for a $20 donation that was no longer worth the effort.

"Very few people seemed to pay it, and actually at the end of the day the Government does give a reasonable sum to a decile 2 school, so it seemed like a waste of energy," he said.

Seventy per cent of school principals in our survey said they would stop asking for donations if the Government goes ahead with a Labour Party election promise to pay an extra $150 per student per year to every state or integrated school that agrees not to ask for parental donations.

A further 21 per cent of principals are unsure, mainly because the Government has not yet spelt out details on what schools will still be allowed to charge for if they accept the $150.

But Auckland Grammar headmaster Tim O'Connor was among the 8.5 per cent of principals who will refuse the $150 offer. Although Grammar parents actually paid only $831 per student in 2016 when the requested donation was $1125, cutting that to $150 each would have cost the school $1.7 million.

"We couldn't operate, actually, if we accepted that," O' Connor said.

Auckland Grammar also received almost $780,000 in donations in 2016, or $309 per student, from charitable trusts associated with the school to help pay for a new $4.6 million classroom block.

Surprisingly, the ministry data shows that the state secondary school with the second-highest donations per student was Tai Wānanga, a "special character" school established by Te Wānanga o Aotearoa in Hamilton and Palmerston North.

Its tumuaki (principal) Toby Westrupp said he asked parents for $1000 a year. But $760 of that was donations of $4 a day for the school to give each student breakfast and lunch.

Epsom Girls' Grammar is asking parents this year to donate $875 (up $25 from last year), Wellington College is requesting $823 (up $18) and Christchurch Boys' High School is seeking $630 (unchanged).

The other schools listed in the ministry data for the top 10 donations per student all ask parents for less than $100, but received donations in 2016 from other sources. Tarawera High School in Kawerau received $100,000 from its local council for a community sports turf on the school grounds, and Rangtikei College said its donations were from "external agencies such as charitable trusts".