Omicron is continuing to spread through West Australian schools and mine sites as the state records 18 new local COVID-19 cases.
Three more workers at BHP's Yandi iron ore mine in the Pilbara have tested positive to the virus, taking the total number of cases at the site to five.
A BHP spokeswoman said they were all close contacts of the initial two cases and had been isolating on site since Sunday.
"They were not believed to have been infectious in the workplace or community," she said on Friday.
"The health and wellbeing of our people, especially those isolating on site, remains critically important. They are under the continued care of our onsite medical team."
There are 21 workers isolating on site and a further 13 contacts isolating elsewhere.
Corpus Christi College meanwhile confirmed a Year 7 student had tested positive, plunging the entire year group into 14 days' quarantine.
The Catholic school's Year 11 cohort is already isolating after an earlier case this week.
"I ask that you would pray for our community members who are now having to self-isolate, and thank you for your support in this time," principal Jeff Allen wrote in a letter to parents.
Four of the 18 new local cases reported by WA Health on Friday are not linked to known clusters and have been infectious while in the community.
The state now has 203 known active cases, all in quarantine.
WA is just days into the school year but hundreds of students and teachers have already been forced to isolate for two weeks after Atwell College, Harrisdale Senior High School and Winterfold Primary School were also exposed to the virus.
The disruption has heaped pressure on Premier Mark McGowan to reduce isolation periods for COVID-infected people and their close contacts.
Mr McGowan has been reluctant to change the settings but this week conceded a move to seven-day quarantine was "not far away".
Teachers and students who come into contact with a positive case but don't develop symptoms will be able to continue attending school when the definitions change.
The Australian Medical Association wants the government to reduce the isolation period immediately.
"It is doing harm to schooling and socialising, and taking parents out of the workforce," AMA WA president Mark Duncan-Smith said.
Test numbers have remained worryingly low during the Omicron outbreak which Dr Duncan-Smith believed was due to complacency in WA.
"I think there is an element that some people are fearful of isolating for 14 days," he added.
West Australians remain no closer to learning when the state's borders will reopen as the third-dose vaccination rate climbs to 42 per cent.
Frontline health workers have rubbished the premier's claim that WA's health system is ready for an inevitable surge in cases.
Prime Minister Scott Morrison on Friday expressed a similar view.
"I can absolutely understand the decision of the premier ... when he would have concerns about whether his health system was ready to deal with the Omicron strain," he told reporters.
