At Al Amanah College in Sydney's west, year three students learned about life all over the world, without leaving the classroom.
"This is a sari and we usually wear it for special occasions."
"You use them to drum on special occasions like Eid."
"We celebrate the same things as in Australia but we celebrate them in different ways."
"Syria is my parents' and my family's country, and it's kind of nice to go there."
The day is a chance to learn about friends and their families.
Almost a third of Australians were born overseas; many more have parents of a migrant background.
Samaya Sahyouni, the Coordinator of Al Amanah College in Sydney's West, says Harmony Day is an important event on the school calendar.
"Their cultural identity is very important to them and they like to celebrate that, so today is a day about diversity."
It's a lesson of increasing relevance beyond the classroom.
23 million Australians have been born in 250 countries, with 270 different ancestries.
Australians speak 240 languages and belong to 120 different faiths.
Karima Al Shelh was born in Australia to Lebanese parents.
Her granddaughter is in kindergarten at Al Amanah College, where she spent Harmony Day teaching the kindergarten students about her background.
"It's important that the new generation need to learn that no matter what colour, what religion you are, we're all human beings."
Harmony Day has been celebrated for almost two decades and it's getting bigger every year.
This year, Al Amanah is one of hundreds of schools around the country, celebrating cultural inclusion.