Darby Borough Police officers staged the emergency drill at Penn Wood Middle School Friday.
The officers slowly made their way through the hallways with guns drawn, as if there were a real threat in the building.
Principal Brian Wilson said the exercise was also a good learning experience for teachers.
"Like all schools, we have an emergency plan," Wilson told Action News. "But it's an awesome opportunity to have the professionals take a look at our emergency plan and critique it so we can make changes. And a chance for my teachers to get an opportunity to see what these professionals do every day."
Delaware County emergency response teams also helped out with the drill.
