Victoria will make face masks mandatory for all children in grades three to six an effort to reduce COVID-19 spread as students start returning to the classroom.
Chief Health Officer Brett Sutton said masks will be required indoors at school for those students, while mask-wearing will be "strongly recommended" but not mandated for younger children from prep to grade two.
"We really want to have these measures in place early on to keep kids in school and to make sure that they are as safe as possible in the school environment," he told reporters.
He said face masks, along with ventilation and other COVID-safe measures, had prevented virus transmission in schools overseas.
"In many states in America, school mask mandates have been put in place and they have helped to reduce transmission," Professor Sutton said.
"It really has been shown that where there are multiple layers of risk mitigation within the schools, that you can keep a cap on transmission and have kids return safely to that environment."
Health authorities and the state government are in the process of drafting the mask rules, ahead of a staged return to classrooms in coming weeks.
Students aged 12 and over are already required to wear face masks at school, unless they have an illness, disability or are exempt.
Melbourne Royal Children's Hospital paediatrician Jane Munro said the mask mandate was "backed by good science" and will help prevent student absence.
"It is simple, it is safe. There are no health risks for a child wearing a mask. It is easy to do and it is also common sense," she told reporters.
"Some people might still be confused about why we need to do this and it is because we want to get kids back to school and keep them there."
Schools in parts of regional Victoria and year 12 students in Melbourne returned to classrooms this week.
More than one million Victorian children will return to 30,000 classrooms across 2276 schools over the next month, with all students expected to return to onsite learning either full or part-time by October 26.
However, none of the COVID-19 vaccines are currently approved for children aged under 12.
As well as mask wearing, Dr Munro said ventilation, physical distancing and hygiene measures are vital for classrooms to return.
"We need to get our kids back at school and keep them at school. We all need to work together as a community to make that happen," she said.
She said RCH, with the support of the Murdoch Children's Research Institute, was developing resources to help children understand what they need to do to return to school.
Professor Sutton also announced a slight change to mask rules for adults from midnight on Friday, allowing masks to be removed to drink alcohol outdoors at a picnic.