How students had to run for cover when teen allegedly walked into library wielding a knife and plunging an entire Aussie school into lockdown

A boy has been arrested in Sydney’s west after a terrifying ordeal in which he allegedly made threats while armed with a knife on his high school campus.

Cambridge Park High School was placed on lockdown around 12.30pm on Friday after reports that a boy began waving a paring knife in the air.

The alarm caused 40 students, who were preparing to leave the library for their next class, to take cover when the boy allegedly walked in with the knife in his hand.

‘I was very scared. When I saw the knife, my heart pounded,” said one student.

“(The boy) started scraping the glass doors with the knife and tapping it with the blade,” another student said 7NEWS.

Children huddled in the corners of the darkened library as teachers managed to ‘push’ the boy out the door.

One student sent a message to his parents and wrote: ‘Mom, we are in lockdown. Someone just came into the library, pulled out a knife and held it up in front of me.”

‘I ran. I’m afraid.’

Other students took cover in the school hallway.

A 12-year-old boy was arrested and taken to Penrith Police Station with a knife seized at the scene

A 12-year-old boy was arrested and taken to Penrith Police Station where a knife was seized at the scene.

Police confirmed no one was injured.

“Staff and police acted quickly to ensure the safety of students. There were no injuries and the school reopened shortly afterwards,” a NSW Department of Education spokesperson said.

‘Support is available for students and staff.’

The boy has treated under the Young Offenders Act.