A session of "show and tell" has forced the evacuation of a school in Newcastle after a student brought a hand grenade into the classroom.
Police said the grenade resembles a World War II "pineapple" and is believed to be inactive, but it will stay on a teacher's desk at Hunter Christian School, Mayfield, until specialists deem it safe.
Students and staff were evacuated to a park near the school, on Kerr Street, on Wednesday morning after the student brought the grenade in to show his classmates, police said.
Newcastle police media spokesman, Senior Constable Tony Tamplin, said it was not yet known where the student got the grenade from.
"It looks fairly old and inactive. Most of what we're doing now is acting in the interests of safety," Senior Constable Tamplin said.
Inspector Gerrard Lawson, from Newcastle City Local Area Command, said all students were safe and well.
"At this time we anticipate an early resolution to this issue but we will await specialist advice as to the safety of moving the item," Inspector Lawson said in a statement.
"I want to warn members of the public that if they have or are aware of military ordnance they should not touch or move it but contact police immediately."
Specialist police and Australian Defence Force personnel will examine the grenade.
Concerned parents can collect their children from the Phoenix Club on Industrial Drive, but students can stay at the sports club until the end of the school day.
Hunter Christian School has students from Kindergarten to Year 12, according to its website.