At least two schools in NSW and three in the ACT received phone calls on Thursday morning. 

NSW Police confirmed they were responding to eight calls to schools and other establishments across the southern region "received simultaneously".

Queanbeyan Police Detective Chief Inspector Neil Grey said they were all "pre-recorded conversations" and similar in context.

Goulburn High School was evacuated shortly before 11.30am but police quickly deemed the threat as a hoax and students returned to class.

Karabar High School in Queanbeyan was also understood to be affected but staff at the school refused to confirm these reports. 

Karabar High School P&C president Dave Lavers said he received a text from his daughter, who is a student at the school, informing him of the evacuation.

"The school is running a debrief for students for what they tell their parents," Mr Lavers said.

"It went well, the kids were calm. We have great teachers, great staff at this school, this is a classic case which goes to show how well looked after our kids are and how professional the staff are." 

Parents also reported evacuations at Braidwood Central School. 

Theodore Public School, Neville Bonner Public School and Forrest Public School also received threatening phone calls, ACT Public Schools announced via Twitter. 

Police attended the three schools but would not speculate on whether the calls were a hoax.

A spokesperson for ACT schools said there was no need for parents to pick their children up at this time. 

Students at Theodore Public School and Forrest Public School returned to class shortly before 12.30pm.

Police allowed Neville Bonner Public School students back inside a short time after that. 

It is the second time in two weeks Forrest Public School has been hit by the phone threats.

Melrose High School was evacuated for two hours on Wednesday after receiving a similar phone call.

Calls to schools in recent weeks have been linked to an international school bomb hoax.

Schools across the world have reported receiving computerised phone messages warning of a device on school grounds.