It's a dilemma that puzzles even the experts - how to pack a school lunch that the kids will eat and is good for them?
Latest results from Census At School, an online survey of more than 23,000 Kiwi students between Years 5 and 13, show that most school lunches contain at least one fresh fruit or vegetable - although the proportion drops in the teenage years.
But AUT public health professor Grant Schofield said most parents still felt forced to include packaged foods, 69 per cent of which were found in a recent study to be "ultra-processed".
"I still give my kids ultra-processed food in their lunches because I can't think of anything else to give them in the context of sending their lunches to school on a hot summer's day," he said.
He said New Zealand should follow the example of many European countries and Japan which provide freshly prepared lunches at school.
The census, an online programme which teachers can opt to use in their classes, shows that the proportion of children with at least one fresh fruit or vegetable in their lunch declines gradually from 89 per cent in Year 5 to 66 per cent in Year 13.
Only 1 per cent of the youngest children don't eat lunch, but that rises to 19 per cent by the final year of high school.
Overwhelming majorities above 80 per cent in all age groups said they did some physical activity after school on at least one day a week that made them "get puffed, sweat or get tired". Examples offered in the survey were "walking to school, biking, swimming, dancing, kapa haka, playing games and sport or just running around".
Ruby Tasmania, aged 15, and her brother Rios, 12, usually have both fruit and vegetables in their lunches at South Auckland's Mission Heights Junior College.
"I have a sandwich with lettuce and cucumber most days," said Ruby. "I usually have two mandarins and sometimes I have a yoghurt."
Rios has "two mandarins and a yoghurt and chips and nuts and crackers".
Both siblings get plenty of exercise. Ruby plays soccer and does kapa haka; Rios plays rugby and netball.
They said some of their classmates "stay inside and play on their laptops" at intervals and lunchtimes, but they were encouraged to go outside.
"Most teachers tell them to go outside and get some outdoor air," Ruby said.
School principal Ian Morrison said the school Wi-Fi was turned off outside class time "so students can get some face-to-face time".
Deputy principal Melanie Kindley said the school had no tuck shop and provided microwaves so students could heat healthy lunches, but teachers did not inspect students' lunchboxes.
"We have seated lunches for the first 15 minutes of lunchtime," she said. "If we didn't have that expectation, we would see a lot of children rush over to the basketball courts as soon as lunchtime starts."
Ministry of Health advice is that children aged 2 to 12 should get at least three servings of vegetables and two servings of fruit a day, along with at least five servings of bread and cereals, two or three servings of milk and milk products such as yoghurt, and at least one serving of meat, eggs, nuts or beans.
It says children aged 5 to 17 should get at least an hour a day of moderate or vigorous physical activity.
Schofield said the healthiest food was "fruit, vegetables, left-overs - anything that their parents can prepare that doesn't come out of a packet".
"The Auckland University study that says 85 per cent of what is sold in supermarkets is ultra-processed and the majority is unhealthy junk food - that's the marker of what's in the food supply, not how many fruit and vegetables kids have in their lunch," he said.
He said it would cost only $100 million a year to provide cooked lunches for every school student.
"I'd endorse cooked school lunches in New Zealand, which is done in the bulk of developed countries."
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