School emergency drills have moved beyond the duck & cover exercises of the Cold War era. Today's drills practice brace students for the presence of armed intruders.

The shooting of 20 first-graders and six adults in Newtown, Conn., has school administrators reviewing and practicing their own emergency plans.

Most states began to require district emergency management plans after the 1999 shooting at Columbine High School in Littleton, Colo. Data compiled by the Education Commission of the States shows preparations vary widely.

On Wednesday, an intruder drill at Cary-Grove High School in Illinois featured the sound of gunfire from a starter pistol.

An October drill at Howe Hall in South Carolina saw victims fall with fake wounds.