They hatched the idea of raising funds to support the work and draw attention to the plight of refugees.
"People being driven from their homes in Syria is arguably the biggest humanitarian crisis of our time," says Zac.
"We are asking everyone to wear no shoes for one day and donate $1."
A ShelterBox typically contains a tent designed to withstand extreme weather conditions, a water purification kit, blankets, tools, and other necessities to help a family survive after a disaster.
ShelterBox was founded in the UK in 2000 and is now supported by international aid agencies and Rotary clubs worldwide.
The Rangitikei students originally set a date of July 5 for SOS day but Elle says they want to drum up more support and spread the word further so they now have their sights for August 11.
"We are sending emails to head students in every New Zealand high school asking them to mobilise their schools," says Elle.
They are also targeting a number of celebrities including Sonny Bill Williams, who has spoken out about the plight of Syrian refugees.
Ministers of Parliament have also received requests and so far the most positive response has come from Education Minister Hekia Parata's office.
"We got a reply saying that the email would be forwarded, so that's encouraging," says Elle.
The trio hope there will be a lot more support from influential people as well as schools, clubs and individuals.
Donations can be made anytime via the web page soles.org.nz and they can be contacted via the Facebook page - sos sole for syria.