The school sent out a letter to families early Friday afternoon confirming the positive case and urging families to follow the advice and guidance of health experts.

In the letter, principal David Shepherd said the school had immediately contacted the Department of Health and were awaiting further information and direction.

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"We will provide information to our community as required and as directed as soon as it becomes available," he wrote.

"This is obviously an unsettling time for us all, but particularly this Clarendon family as they navigate the next few days."

It is unknown whether the family affected live in Ballarat or where the family member was infected.

The news comes as Bacchus Marsh Grammar confirmed four staff at the school have now tested positive after an infected staff member attended a professional development day on Monday.

The initial case had not been at the school when students were present, but the recently confirmed cases include staff who have been in direct contact with students.

"We currently have a significant number of staff tests back but given the size of the school we are still obviously waiting on a number from yesterday," said Bacchus Marsh Grammar principal Andrew Neal.

The whole of the Maddingley Campus has now been designated a tier one site meaning anyone who attended must isolate for 14 days and take a COVID-19 test.

"Those students who have been deemed to be in close contact with the teachers involved will be contacted directly by the department. We will also endeavour where we are able, to provide directly impacted students with as much information as possible," Mr Neal said.

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"I would urge anyone in the community who is showing symptoms to get tested and I reiterate the need at this stage for all students to remain in isolation at home. This is an enormously anxious time for the whole community.

"To a certain extent we are going to cope with this situation best by accepting the constraints we now face, understanding that information may be a little slower than we would like and accept that there are a team of people at school and the DHHS that are working to make the best of the situation for everyone."

Victorian exposure sites:

The cases come as health authorities reported six new cases on Friday, all linked to the current outbreak. The state's 24 active cases from community transmission include four connected to the MCG and two to Young & Jacksons pub.

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