Ministry of Education head Peter Hughes has made a plea to all schools, asking them to consider ditching sugary drinks in favour of water to help tackle childhood obesity.
Yendarra School in Otara went water-only 10 years ago, and principal Susan Dunlop told Newstalk ZB there was no downside.
She said the children are easier to teach and their dental health is better than many other nearby schools.
She said one parent complained when the school initially went water-only, but now everyone understood the benefits.
The Heart Foundation has applauded the Ministry of Education for the call.
Education setting manager Justine Munro said research proved poor diet was closely associated with low academic achievement, and schools that had gone water-free had seen improvements in behaviour, concentration and attendance.
Ms Munro said children also took the healthy drinking policy home, which helped influence parents to change their ways too.
Meanwhile, one Christchurch principal has made a splash in an effort to encourage other schools in the city to go water-only.
This afternoon West Spreydon School principal Marriene Langton let students tip a bucket of water over her head and spray her with water bottles.
The school has been water-only for 10 years and she hoped the stunt would raise awareness about the many benefits.