Students at the South Sioux City High School and Middle School were placed in a brief lockdown during the noon hour Monday.
School officials say a South Sioux High School student made a verbal threat around that time and walked out of class.
Police were summoned and the schools went in to lock down at that time along with Cardinal Elementary.
The student was detained by law enforcement within ten minutes.
School officials say the high school was to remain in lockout as a precautionary measure until the daily schedule was adjusted and set.
No safety threat exist at any of the buildings.