Threatening phone calls which led to a number of schools in Victoria's east evacuating students on Friday were a hoax, police say.

Schools in Craigieburn, Berwick, Morwell, Lakes Entrance, Sale and Cowes on Phillip Island were evacuated following the calls.

Victoria Police said they were aware schools in a number of other states and countries had also received similar phone calls in the past 24 hours.

But police later said they were "satisfied that there are no imminent threats to schools".

"Victoria Police can confirm it is treating the threatening phone calls received by a number of Victorian schools today as a hoax," they said in a statement.

A police investigation into the origin of the calls is ongoing, but police said they were not terrorism-related.

'Terrifying' beginning to school year

Hundreds of students at Sale Primary were relocated to another school and were collected by parents.

It was the second day back at school for many of the students.

A Victorian Education Department spokesman said the incident was taken seriously.

"The safety and wellbeing of our students is always our number one priority," he said.

"All schools have emergency management plans which include evacuation plans, and the affected schools have enacted their plans this morning."

Amanda Renda, whose son attends Craigieburn Primary School, said the incident added stress to the start of the school year.

"The kids were fine, they didn't know what was going on," she said.

"They were happy which is reassuring. It's just not a good thing to go through as a parent - it's quite terrifying."

The principal of Berwick Lodge Primary School, Henry Grossek, told 774 ABC Melbourne they got a call from unidentified male at about 11:24am.

"The prep children - it was their first day at school, it was a really ripper of a day," he said.

"The kids start school, I reassure parents I've got a safe school for them and here we are evacuating.

"They come to pick the children up at 12:45pm on the first day... we decided the police would organise the streets to be blocked so that all the parents would be channelled into a car park not on our school [grounds].

"All the prep parents then would pick their children up there at 12:45 which they did."

In New South Wales, police confirmed officers had been called to schools at Woolooware, Sutherland, Penrith, Mona Vale, Richmond and Lake Illawarra.

Officers said those schools had either been evacuated or were in lockdown.