A two-hour lockdown at Houston ISD's Sterling High's was lifted after noon, following a physical altercation between students that ended in a stabbing, a district official said. Houston ISD police fielded traffic as frightened parents lined up to pick their children up at the Martindale Road campus in south Houston Wednesday afternoon.

The southeast Houston school was one of two placed on lockdown Wednesday because of incidents involving knives. A student at Elsik High School was in possession of a kitchen knife.

Under Texas law, threatening a school is a felony offense, even if it isn’t acted upon. According to a release from the Texas Department of Public Safety, students who make threats to a school can be arrested, have a permanent criminal record, face heavy fines, and possibly go to jail.