Researchers say measures taken in the wake of school shootings are often ineffective -- and that when promising measures are tried, they often don't get enough funding to work. Read more about prevention of school shootings:
- "What Can Be Done About School Shootings?: A Review of the Evidence"
- The study of school shootings by the U.S. Secret Service and the U.S. Department of Education: "The Final Report and Findings of the Safe School Initiative"
- Advice for schools from the Secret Service study: "Threat Assessment in Schools: A Guide to Managing Threatening Situations and to Creating Safe School Climates"
From the NBC News archives:
- Does every school need a metal detector?
- Threat assessment approach seen as lifesaver
- 10 myths about school shooters
More from NBC News Investigations:
- Newtown report: Lanza had no clear motive, was obsessed with Columbine
- Teen suspect in murder of teacher Colleen Ritzer left 'hate' note, documents say
- Jimmy Breslin, the gravedigger and 'the bleary day' they buried JFK
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