The operators of a Melbourne school where dozens of students and staff have caught COVID have shrugged off criticism for flouting lockdown rules and remaining open.

Victorian authorities are investigating the outbreak at the Fitzroy Community School in Fitzroy North, which has repeatedly ignored lockdown restrictions and invited parents to send children into class.

COVID-19 Commander Jeroen Weimar confirmed on Monday that 31 students and staff had so far caught the virus, while 189 close contacts have been forced into self-isolation.

The school, which describes itself as an “independent, alternative primary school”, has been listed as a tier one exposure site for several days.

It has about 120 students. About 60 have reportedly been in class each day, despite Melbourne’s lockdown rules allowing only children of permitted workers and those who are vulnerable to continue with face-to-face learning..

School founder Faye Berryman told ABC News 24 primary-aged children have “a strong resilience to COVID”.

“We are not lunatic fringe, we are pretty conservative, deeply-thinking people,” she said, reading a statement through a window at the school.

“Children’s emotional wellbeing, their feeling of insecurity, the unpredictable long-term psychological danger of raising them under a mantle of fear are the price we pay for not having children at school.”

The school’s principal, Ms Berryman’s son Tim, has been a vocal critic of school closures during lockdowns. He reportedly invited all families to keep sending children into classrooms during Victoria’s fifth lockdown in July, until a visit from health officials prompted a change of heart.

The school has remained open to pupils who cannot study from home.

“There are some whose parents fall into a particular category or worker or who are considered vulnerable but I think the reason we have had so many come to school is because we’ve been offering the full teaching and learning experience,” Mr Berryman told The Australian on Monday.

“We’re not just sitting the students in front of a screen all day.

Victoria had another 473 local virus cases on Monday, the highest yet in its latest outbreak. It has 3507 active cases – 87 per cent in people aged under 50.

State Health Minister Martin Foley described the burgeoning outbreak as a “pandemic of the young and the unvaccinated”.

All but 38 of the latest cases are in Melbourne’s northern and western suburbs, which had 338 and 97 cases respectively.

Mr Foley said 89 per cent of the 157 Victorians battling COVID-19 in hospital were unvaccinated, while 11 per cent had received one dose.

Shadow education minister David Hodgett said the Victorian opposition did not support breaking rules but he understood Fitzroy Community School’s actions.

“The government has not put out a single plan. There’s no certainty, there’s no hope,” he said.

The state government is continuing to develop a roadmap out of lockdown, including a plan to return students to classrooms in term four.

There are more than 450 COVID cases linked to Victorian construction sites. Photo: Getty

Elsewhere, Victorian authorities announced a construction site compliance and vaccination blitz on Monday, with the construction sector warned it could lose its COVID-19 lockdown authorised worker status.

Treasurer Tim Pallas announced the four-week enforcement blitz would begin on Monday, saying the construction industry stood at a “critical juncture” as one of the few sectors still operating.

“We’re seeing increasing case numbers coming out of that industry linked to this workforce,” he said.

“What’s become clear to us is that the construction industry remains a major source of transmission.”

Of Victoria’s 3507 active cases, 13 per cent are directly linked to construction sites.

Victorian authorities are particularly concerned by their geographic spread, with the average infected construction worker living about 20 kilometres away from their workplace.

That compares to four kilometres for the average case in the outbreak.

While the majority of sites are following rules, including workers donning masks, Health Minister Martin Foley said it was clear the industry needed to improve.

“It doesn’t take much for this highly infectious Delta variant to get from a highly mobile, younger, under-vaccinated workforce into outer suburbs, into the families and communities of those suburbs, and, as we have seen, into the regions,” he said.

Nearly 6000 checks have already been carried out, and Mr Pallas said WorkSafe inspectors would adopt a “zero tolerance” approach.

From July 1, on-the-spot fines for authorised worker breaches increased to up to $1817 for individuals and up to $10,904 for businesses.

In concert with the enforcement blitz, four major Victorian vaccination centres will allow construction workers to get a jab without a booking from Monday until September 26.

A further 20,000 further priority Pfizer appointments will also be made available to construction workers at all state-run hubs, except for drive-throughs.

Melbourne’s large-scale construction workforce is capped at 25 per cent, but it was previously announced that figure will double once 90 per cent of workers have had one vaccine dose.

Meanwhile, most regional Victorian train services remain suspended on Monday as 300 V/Line employees isolate after five positive tests among drivers and operational staff. Coaches are replacing most services.

-with AAP