A classroom building on the western side of Cosgrove High School was burnt through in Hobart's Glenorchy last night (Saturday).
The fire, which is classified suspicious, was reported in just before 8pm and caused large amounts of smoke and some ash.
Cosgrove High will be closed tomorrow (Monday) as a safety measure.
Glenorchy Mayor Kristie Johnston reached out to the school community on their Facebook page inviting it to reach out if there is anything the council can do to help.
Anyone with information in relation to the fire, or suspicious activity in the area at the time, is asked to contact police on 131 444 or Crime Stoppers on 1800 333 000.