arming teachers works, here are two examples

Pearl High School shooting

The incident began on the morning of October 1, 1997 when Luke Woodham fatally stabbed and bludgeoned his mother, Mary Woodham, as she prepared for a morning jog. At his trial, Woodham claimed that he could not remember killing his mother.

Woodham drove his mother's car to Pearl High School. Wearing an orange jumpsuit and a trenchcoat,^[1] he made no attempt to hide his rifle. When he entered the school, he fatally shot Lydia Kaye Dew and Christina Menefee, his former girlfriend. Pearl High School assistant band director, Jeff Cannon, was standing five feet away from Dew when she was fatally shot. Woodham went on to wound seven others before leaving, intending to drive off campus and conduct another shooting at the nearby Pearl Junior High School. However, assistant principal Joel Myrick had retrieved a .45 pistol from the glove compartment of his truck and subdued Woodham inside his mother's car. Then Myrick demanded "Why did you shoot my kids?" to which Woodham replied, "Life has wronged me, sir."^[2]

http://en.wikipedia.org/wiki/Luke_Woodham

Parker Middle School dance shooting

The Parker Middle School dance shooting was an incident that occurred on April 24, 1998 at a restaurant in Edinboro, Pennsylvania, United States. 14-year-old Andrew Jerome Wurst fatally shot 48-year-old John Gillette, and wounded another teacher and two students^[1] at Nick's Place (a nearby restaurant) during an 8th grade graduation dance.^[2]

The shooting ended when the owner of Nick's Place, James Strand, intervened and confronted Wurst with his shotgun, ordering him to drop his weapon and later holding him at bay for eleven minutes.

http://en.wikipedia.org/wiki/Parker_Middle_School_dance_shooting