A teenager has been taken into custody over a fire that damaged part of Comet Bay College in Secret Harbour.
Fire crews were called to the high school on Allatoona Avenue around 7.25pm on Thursday to find a two-storey building fully engulfed.
It took them nearly two hours to bring the blaze under control.
The school has confirmed several classrooms have been damaged.
No one was injured but a 15-year-old boy has been taken into custody.
Parents have been advised the school is closed today.
The fire scene remains under police guard.
Arson Squad detectives will be returning to the scene this morning to investigate the cause of the fire.
Anyone with information regarding this incident is asked to call Crime Stoppers on 1800 333 000 or report the information online at www.crimestopperswa.com.au.
Rewards of up to $25,000 are available for information that leads to the identification and conviction of an arsonist.
Police issue 31,000 driving infringements in first month of new AI cameras
Works underway on Rockingham and Safety Bay High School redevelopments
New measles exposure sites revealed in Bunbury
Dawesville man charged after allegedly leaving his elderly Great Dane to suffer painful conditions
Good Samaritan sought by police after helping teen during robbery in Baldivis
Under-16s social media ban now in force
Desperate search continues for missing Bunbury FIFO worker
Passengers now able to use credit, debit cards to tag on and off WA's public transport
New floating jetty speeds up emergency response times for Marine Rescue Mandurah