A 15-year-old girl has been charged over an alleged bomb hoax at Cairns State High School on Monday.

Police said the teenager entered the school grounds at midday and assaulted two staff members.

A 15-year-old girl has been charged over an alleged bomb hoax at a Cairns school on Monday. Credit:Tom Threadingham

It will also be alleged the girl made threats against the school, causing it to be evacuated.

Police located and arrested the girl and determined the threat to be unsubstantiated.