Hundreds of children at St Clair Public School have been involved in a major security scare when a home made bomb device was detonated.
Police described the bomb as a small explosive device.
It was said to have been thrown over the fence, into school grounds, from a nearby laneway.
The school enacted an emergency plan and 240 students were sent home while police and bomb squad investigated the scene.
Police have not identified the chemical used in the explosion, they believe the bomb was more of a dangerous prank than an attempt to kill.
According to reports, the school has previously been attacked like this and firefighters have been called here on numerous occasions after lit matches and cigarette butts were thrown over the fence.