Police conducted a helicopter search after a window was broken at Stowmarket High School.
Between 10.30pm and 11pm on Saturday, a window was smashed but no entry was made and no property stolen.
The caretaker was alerted after an alarm at the school went off and police were immediately notified.
Air support was called in to search the area around the school but nobody was located in the vicinity.
If you have any information about the incident please call police on 101.