The Army has removed an old grenade from a school in north Queensland after a child brought the item to class.

Staff at the Calen District State College near Mackay alerted police to the incident early this morning.

A police spokesman says the school was evacuated and the grenade was buried at the school's oval.

A team from the Townsville army base removed it this afternoon.

A Defence spokesman says the grenade was missing a mechanism, which lessened the risk of it exploding.