The Education Department's policy change was inspired by an 11-year-old student known as Sophia who, with the help of her mother, Krystina Myhre of Perth, wrote a letter to the state's education minister, Sue Ellery.
"My daughter and her friends have been quite unhappy about it for some time," Myhre told the New York Times in an interview.
The restrictive dress code understandably made it challenging for Sophia and the other girls at the school and in the region to participate in athletic activities outside of gym class.
In her letter, Sophia wrote, "I think it's really unfair that my brothers have been allowed to wear shorts, and all through [school] I haven't been allowed to except when I have sport."
"I really love kicking the footy, netball and doing handstands at recess and lunch. It is annoying doing these things in a skirt."
The new change allowing girls to wear pants and shorts to school does not apply to private schools, although several private educational institutions in Perth have indicated that they will implement similar policies.
"We are introducing trousers for girls next year," said Robert Henderson, principal of John XXIII College.
"It's certainly not throwing out the traditional uniform," he added.