Finley Public School was closed on Monday after “significant damage” to all but two of its buildings.
Between 6.30pm Friday and 7.30am Sunday, buildings at the school were broken into.
Murray River Police District said several doors were kicked in and windows were smashed.
Classrooms, a storeroom, staff room and library were ransacked, while the outside of the buildings were vandalised with graffiti.
Two laptops and an interactive smart board were also destroyed.
The damage was discovered by the school cleaner on Sunday.
The school was closed on Monday due to damage, but reopened to students yesterday.
Officers attached to Murray River Police District established a crime scene for forensic examination, and have commenced an investigation.
As investigations continue, police urge any witnesses or anyone with information to contact Tocumwal Police on (03) 5874 9399 or Crime Stoppers on 1800 333 000.