The ukulele has been described as a "happiness machine" and Room 5 at St Joseph's School in Otahuhu totally agree. Their cheery classroom sounds like a joyfully humming beehive, as two dozen 10-year-olds - sitting legs crossed, socks pulled up, hair neatly plaited - twang happily to themselves. Then, at a word from their teacher, they stop doing their own thing and start strumming a Samoan song, Le 'Aute.
They sing along - something you can't do while playing a recorder (the musical instrument du jour of my school days).
Playing is "like taking a vacation", says Stella, one of the pupils.
Room 5 started "air ukulele" lessons only three months ago - to keep the cacophony down - and they now sound remarkably good and in unison. "With three chords you can play thousands of songs," William, another pupil, says knowledgeably.
They're doing something I never learned to do - reading chord charts - and it's not often you get taught in primary school some know-how that many adults do not have. (For the record, I played a mean euphonium for three weeks in high school.)
I'm at St Joseph's to find out why the ukulele's popularity has soared like a soprano in recent years, and it turns out the formula is as simple as three chords: the instrument is cheap, easy and makes people happy.
It's even more popular in New Zealand than elsewhere; Room 5 at St Joseph's is part of the Kiwileles school group, which is having an open rehearsal at 1.30pm today in the Cloud on Queens Wharf. Everyone is welcome for a singalong (the words will be on screen) while 1000 children play everything from a "disco version" of Beethoven's Fifth to Kiwi pop songs.
The group will be even larger at the New Zealand Ukulele Festival on November 26, Election Day, with 2500 children from 116 schools.
They're billed accurately as the Biggest Ukulele Orchestra in the World, but already this year smaller groups of Kiwileles have entertained at the Pacific Leaders Forum and the New Zealander of the Year awards, and accompanied The World in Union anthem at the Rugby World Cup opening ceremony at Eden Park.
Mary Cornish, chairwoman of the New Zealand Ukulele Trust which organises Kiwileles, says the ukulele's relevance to Pacific and Maori cultures is part of the reason it's so popular here. Children take instruments home and parents remember how they used to play themselves.
"Everyone starts joining in and you've got people singing together again," says Cornish.
Is it no longer considered, well, kitsch? "Oh, it's no joke," says Cornish, who owns five ukuleles. "It's like a lute or mandolin. It's a constant quest for the perfect sound."
Remarkably for a volunteer, donation-based organisation, the trust puts out songbooks and recordings, runs teacher workshops and has so far donated ukuleles to 48 schools. It gets no government funding for this; because of the focus on reading and mathematics, there is now no targeted funding for primary school musical education in New Zealand.
This short-sighted policy is in the face of a lot of published evidence that music enhances all education. Unsurprisingly, St Joseph's teacher Juliana Ngiam has seen a change in her pupils' behaviour since the ukuleles appeared.
Formerly disruptive pupils will do anything to be allowed to play and quiet dreamy ones have become focused class contributors.
Reasons for happiness indeed.