Two juveniles have been arrested over the vandalism at Ballina High School last week that resulted in an estimated $30,000 damage.
Richmond Local Area command police said further arrests were expected.
About 50 glass windows were smashed in the attack, which happened between Between 11:50pm on Thursday 8 September and 4.45am Friday 9 September.
The vandalism affected eight classrooms, and forced the closure of the school for the day while police investigated.
More details to come