North Platte High School (NPHS) was placed on lockdown early Tuesday morning.
According to a press release from North Platte Public Schools, the high school was placed on a lockout as part of "Standardized Response Protocol in order to protect students and staff against a potential threat outside of the building."
They said the lockout was announced at about 9:50 a.m. and was lifted at around 10:50 a.m.
North Platte Public Schools said students attended classes normally, but no one was allowed to enter or exit North Platte High School during the lockout.
"NPHS Administration, along with law enforcement, received possible concerns of a threat outside of the high school," Tami Eshleman, Associate Superintendent, said "North Platte High School activated the Standardized Response Protocol. More information on this protocol can be found in the student-parent handbook."