Delaware State Police were dispatched at 10:30 a.m. to the Delaware Academy of Public Safety and Security Charter School, located at 801 North Dupont Highway in Wilmington Manor.
The threat was written on a note found in a bathroom.
Students were evacuated while the school was searched, but allowed to return to the school shortly before noon.
Police say there was a similar incident at the school last week. Both incidents are under investigation.
Delaware Academy of Public Safety and Security Charter School is a high school with over 300 students enrolled.
