The school, located at 2102 S. Broad Street, went on lockdown at 9:30 a.m. after a 9mm magazine with one live round was found in a student's backpack while the 17-year-old passed through the metal detector.
The security office detained the student and the magazine was recovered. A K-9 also searched the area.
The lockdown has since been lifted. No other information has been released at this time.