(CBS News) When the school year begins, more teachers will be armed. Since the shooting at Sandy Hook Elementary School more than a year and a half ago, nine states passed laws allowing teachers to have firearms in school.

It may look like target practice at a police academy, but these men and women are teachers. They’re learning to defend their students against an increasingly common threat: a school shooting.

Their faces cannot be shown because they’re the classroom equivalent of an air marshal on a plane. They carry their weapons anonymously.

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