"We have been working with the Heart Foundation and looking at healthy food choices as well, so students are attuned to eating and drinking the right things," said Ms Watson.
"Parents have told us their children have objected to some items in their lunchboxes, saying they are not healthy."
Ms Watson said children were more able to learn when they were well hydrated, and drinking plenty of water also helped recovery from illness so there were fewer absences.
Rutherford Junior High principal Diane Henare has been encouraging water drinking at the school since she arrived in August 2014, and aims to put a formal policy in place.
"All the students are asked to bring their drink bottles and put them out on their desks first thing," she said.
Despite the Ministry of Health giving Whanganui water an Aa grading, many agree that the taste is not great.
Ms Henare said the school had added lemon slices to improve the flavour.
"We also qualify for the Fruit in Schools programme and we have added sliced fruit to jugs of water and students enjoy that."
Orautoha School in Raetihi had also been water-only for some time and principal Robyn Brider said the benefits were numerous. "The children are able to focus longer, they have more energy, they stay hydrated throughout the very warm summers and water is so much healthier for their teeth and bodies - and it's free."
About 10 per cent of New Zealand schools are water-only, and the Ministries of Education and Health are encouraging all schools to consider banning sugary drinks from their premises.
Healthy Families Whanganui Rangitikei Ruapehu team leader Debbie-Jane Viliamu wants more local schools to become water-only.
"It is a proactive way to make healthy change for the benefit of our children," she said.
The Healthy Families team will work with schools, marae, churches, businesses, sport clubs and others to support healthy changes.
Visit www.healthyfamilieswrr.org.nz.
