The father also encouraged those to pray for the other boy involved, who remains in critical condition in hospital fighting for his life.
Kaitoke School Aotea said they were “incredibly heartbroken to hear this and our heartfelt love and condolences” went out to the family and wider community
The school would be closed on Friday to allow the community to grieve, and on Tuesday so staff and students could attend the boy’s service.
“There are very few words that can describe what we are feeling and going through,” principal Leanne Eloff said in the Facebook post.
The pair were flown by rescue helicopter to Starship Children’s Hospital in critical condition from Medlands Beach on Sunday afternoon.
One of the boys, aged 14, was found with his legs sticking out of the sand and was pulled out with the help of a vehicle, Stuff reported.
The other, a 12-year-old, was completely buried and was not breathing by the time he was extracted.
Beachgoers and emergency services, including staff from two rescue helicopters, scrambled to dig the boys out.
The devastated community of Great Barrier Island has banded together and a Givealittle page has been made to support the families of the boys.
The page describes a beautiful day at the beach which turned into a tragedy.
“Please, please, if you can, donate to this tragic cause - support the boys through their battle, support the whānau through theirs.
“The whole community of Great Barrier Island is devastated and banding together with solidarity and strength of love to support them,” the page’s creator, Aroha McGeady, wrote.
The page had raised a little over $52,000 at publication time.
“Our thoughts are with the boys and their families,” a rescue helicopter spokesman said.
Great Barrier Local Board chair Izzy Fordham earlier said that she was “very aware” of the incident and told the Herald it was a “horrid time”.
Great Barrier’s sand dunes extend across the eastern coast of the island, from Medlands to Whangapoua.
One Great Barrier Island resident said there were ocean-side sand dunes that were left exposed after the recent severe weather events, and locals were worried about them.