Montgomery County Police say officers responded around 10:00 a.m. to Watkins Mill High School in the 10300 block of Apple Ridge Road for a report of an assault.
Officers at the scene, learned that two students exited the school building to fight each other, and one of the students pulled out a knife.
Police say one of the students was taken into custody at the scene.
No injuries were reported during the incident.
The school was briefly put into a shelter in place as police responded to the scene. That order has since been lifted.
Officials say the school has been secured, and there is no ongoing threat.
The incident remains under investigation.