Campbelltown police officers were called to Macquarie Fields public school around 12.45pm yesterday, following reports that a classroom window, had been smashed by a "metal projectile".
A crime scene was subsequently set up at the school, which is located about 40km south-west of Sydney CBD.
Investigations revealed that was small calibre bullet, which was seized and will be forensically examined by specialist police officers.
No students or staff at the primary school were injured as a result of the incident.
