The Cumberland Valley School District said it is investigating rumors of potential violence at the high school.
In a statement sent to parents and posted on its website, the district said the rumor surfaced on Thursday and indicated that someone is planning to bring a gun to school on Friday, December 21.
Similar rumors have surfaced in other districts in the area.
The district said the Silver Spring Police Department has been made aware of the rumor and is assisting in the investigation, which includes interviews to track the origin of the rumor.
Officials said they are confident that the rumor is not based on an actual threat, and that students and staff should feel safe.
Police will provide an added presence on the campus and in the high school on Thursday and Friday, and all exterior doors will remain locked throughout the school day, the district said.