The move is aimed at protecting young eyes from the sun's dangerous ultraviolet rays, and education authorities say they are considering adopting the plan at all state schools.
The headmaster of Sydney's Arncliffe Public School, where sunglasses are now compulsory for children from kindergarten through Year 6, said they had no problems wearing the glasses in the playground.
The "sunnies" as they are called in Australia, would soon become "routine" for the pupils, Stephan Vrachas told commercial radio.
The education minister of New South Wales state, of which Sydney is the capital, said the government would consider making sunglasses compulsory in all public school playgrounds.
"It is conceivable that in certain environments it might be appropriate to wear sunglasses when they are playing in the sun," John Della Bosca told reporters.
Excessive exposure to the sun's ultraviolet rays, already blamed for skin cancers, can also lead to cataracts, experts say.
A specialist at Sydney Eye Hospital told the national AAP news agency that wraparound glasses were the best for eye protection and children should be encouraged to wear them from the age of three or four.
Sunglasses were particularly important in summer, when ultraviolet exposure was up to five times higher than in winter, said Con Petsoglou.