A reinforcement system and method for a door having a window provides for a window shutter that slides into a position covering the window during a shooting incident. An elongated bar has one end pivotally supported by a securing bracket, which is attached to a wall adjacent the door. A release pin is attached to the securing bracket; it normally supports the bar in a vertical stored position. A holster is secured to the wall on the opposite side of the door in alignment with the securing bracket. The shutter, the securing bracket, and the holster are formed from a ballistic resistant material. During a shooting incident, the user moves the shutter to cover the window, removes the release pin and pivots the bar into a horizontal position barring the door. The free end of bar is received in the holster, thereby reinforcing the door independently of the door frame and door hinges.