South Australia has recorded 1,138 new COVID cases and four deaths.
The deaths include a woman in her 60s, a man in his 70s, a woman in her 90s and a woman older than 100.
Chief Public Health Officer Nicola Spurrier said with school resuming, children were beginning to make up a higher proportion of positive test results.
Professor Spurrier said the latest numbers took the total active cases to 13,292.
"We still have 219 people in hospital and 18 unfortunately still in ICU with five people ventilated," she said.
"If you've got young children, you've had your kids back at school this week. We are still seeing slightly increased numbers of children turning positive out of those testing numbers which is not of course unexpected."
Earlier, the state's Department for Education said four primary schools — Stirling North in Port Augusta, Craigburn, Mitcham and East Marden — had been affected by classroom closures linked to COVID-19.
"We've got four primary schools that are impacted across the state, and these are classroom closures, not school closures," chief executive Rick Persse said.
"These are all actually reception classes where we've had sort of multiple cases.
"With the prevalence of cases in a couple of these classrooms, the decision's been taken to close that classroom for four days and strongly recommend that parents have their children PCR tested. We look to be back in business face to face on Monday."
Unvaccinated police to remain off work
Meanwhile, South Australia's police union has said there is no reason why dozens of unvaccinated officers could not be doing work from home.
Police Association of South Australia president Mark Carroll said about 70 union members were currently off work after refusing to receive a vaccine.
"The number alone is like a whole patrol base being taken away," he said.
"They're sitting at home, they want to assist, they're long time police officers, very experienced."
He said the current situation — along with positive cases and isolation requirements — was putting pressure on the workforce, creating a "full-blown staffing crisis".
"We know that COVID-19 spreads both through vaccinated and unvaccinated people so we know that protocols could be put in place, we know that, for example, prison officers who are unvaccinated are back at work in a prison. The rules are changing," Mr Carroll said.
Mr Carroll, who has been fully vaccinated, said it was "reasonable" for unvaccinated staff to want to return to home duties.
But Deputy Commissioner Linda Williams said allowing unvaccinated members to return to work could encourage the spread of anti-vaccination sentiment within the force.
"I have been asked — well why can't they do other duties and work from home?" she said.
The Deputy Commissioner said police had "an obligation" to provide a service to the community and "have people in the workplace able to do the job".
"At the moment in terms of reducing transmission, their personal safety and safety of the public and other officers, they're not able to come to work," she said.
"It's been a fine balancing act and that's the position that we've taken at the current time."
Premier Steven Marshall said there were "very few mandates" in place in South Australia.
"Vaccination is our pathway to reduce restrictions in SA," he said.
A mandate came in for Metropolitan Fire Service staff to have had at least one COVID-19 vaccination on Sunday.
