"These are 6 and 7-year-olds so writing is something we do every day and if we have a good excuse to write a letter then we'll do it," Ms Smith said.
"When we showed them the postcards most of them didn't actually know what they were and when we got them writing we had to cut back their words because they were writing whole pages in their exercise books."
Year 3 pupils Adonai Schuster, 7, Jasmine Head, 7, and Ocean Puaha, 7, said they loved writing on the postcards.
"It's cool because it teaches you to write properly and if you don't know a word you can sound it out," Jasmine said.
Ocean said he liked writing every day because it "makes you brainier".
Chapman College and Malfroy School are the two other schools listed as taking part in the initiative.
Warehouse Stationery chief executive Pejman Okhovat said research had shown when students practised writing by hand they learned how to read and write more quickly and accurately.
" In times when traditional letter writing is becoming a lost art, we think it's important to continue to encourage Kiwi children to keep it alive."
He said the company would also be launching its My Favourite Words campaign this month. New Zealand children and their families will have the opportunity to submit their favourite word and reason why, with the chance to have their handwritten sentence selected to appear in the final notebook.
Proceeds raised from the notebook will be donated to the Warehouse Stationery Scholarship Fund - an initiative with the Salvation Army which helps young New Zealanders achieve their tertiary study goals.
- For more information about Get New Zealand Writing and Favourite Word, visit www.warehousestationery.co.nz.