"The competition helps make young people aware of world issues, while giving them an opportunity to explore their creativity.
"I think they are very proud of what they've done - seeing them hung up in the library was a big boost."
This year's competition theme was "Peace, Love and Understanding," with the children using recurring motifs such as doves of peace, olive branches, peace signs, and yin and yang symbols.
According to worldwide criteria, all posters must be two-dimensional, done in either pastel, coloured pencil or felt tip, and be no larger than 50cm by 60cm.
The Greytown Lions committee judged the children's artwork and the winner was 12-year-old Eddie Doherty, with her intricate representation of a dove of peace and a globe made up of nations' flags.
Her entry will be sent to Auckland and judged alongside those from other New Zealand schools, with the winning poster sent for international judging to the US.
The People's Choice Award, as voted by the Greytown public, went to Year 7 pupil Coco Fail-Bosswell for her colourful work of hands exchanging a token of friendship.
The students' posters have been on display since Monday.