One arrest as threats continue to schools

A teenager has been arrested over a threatening call to a Canberra high school amid continued, unrelated threats to schools across four states.

Schools in both NSW and South Australia were disrupted on Thursday, including some being evacuated.

It followed earlier threats against schools in NSW, Victoria and Queensland.

Experts believe the threats could be the work of teenage hackers using online programs to make untraceable calls and create computer-generated voice messages but could also be the work of criminals.

Police and education authorities have been tight-lipped about their investigations but say they are taking the threats seriously.

An ACT police spokeswoman said the call to the Calwell High School on Wednesday was not linked to the other threats but still sparked an evacuation.

The teen is expected to be charged and appear in the ACT Children's Court next week.

The arrest came as Federal Education Minister Simon Birmingham said federal security and intelligence authorities had joined state police and education department investigations to trace the source of the anonymous threats.

He also warned on Thursday against people making copycat calls.

"They are at high risk of getting caught and there are very serious penalties for making such foolish threats," he told the Nine Network.

"The important thing for parents to understand and appreciate is that we are taking these matters extraordinarily seriously."

In NSW on Thursday police confirmed threats to schools at Kings Cross, Green Valley, Botany Bay and Penrith.

Tempe High School was also evacuated due to threats, according to a parent of a student.

At least three Adelaide schools received threats, including Adelaide High School in the CBD and others in the eastern suburbs.

Hundreds of students were removed from Adelaide High after a receptionist received a phone call warning of a bomb at around 11.30am.

Police confirmed the threat was a hoax and students returned to their classes about an hour later.