About 80 per cent of school kids aren't protected from the sun during lunch, according to research from Otago University.
It is the worst time of day to be exposed to harsh UV rays.
Auckland Primary Principals' Association Kevin Bush told TVNZ 1's Breakfast show that he was surprised by the findings.
He said it could be due to kids losing their hats and kids being unenthused about wearing them.
Mr Bush said most schools have a no-hat no-play policy but some schools do not have enough shaded areas.
"I think we've just got to make hats cool."
He said parents needed to make sure their kids were wearing hats outside school too.
The Otago study looked at 1300 children from eight Wellington schools.
Central New Zealand was rattled by a magnitude five earthquake last night, centred 25km south-east of Nelson.
The quake struck at 9.30pm yesterday at a depth of 74km, according to GeoNet.
According to the GeoNet website more than 8842 people felt the "light" shake.
It was felt widely at the top of the South Island and the bottom of the North Island - as far north as Taupo and as far south as Dunedin.
Nelson City Council has called the earthquake "a nice little shake there as we all settle down for the evening!"
Others took to twitter to mention they had felt the jolt, with one user tweeting, "well that was a little bit like a truck hitting the house."
There are no reports of damage in Nelson.
The council is reminding residents to be prepared and refresh their emergency plans with information from Nelson Tasman Civil Defence's website.