More than 20 mosaic tiles painted by Year 4 pupils at Kawaha Point Primary School were smashed in a "malicious" attack on Queen's Birthday weekend.
The tiles were part of the native area, a vegetable and native plant garden where pupils are taught about sustainability and the environment.
The tiles had only been displayed since April, when the garden was officially opened, before the vandals destroyed them.
Kawaha Point Primary School principal Andrew Sinclair said the vandalism was "out of the blue and very disappointing".
"It was devastating for the kids who had worked so hard on the tiles. The attack was purely of malicious nature with no personal gain other than to ruin some kids' work so it was really disappointing."