Some schools already arm teachers. Here's how they do it.

Since the 2013 massacre at Sandy Hook Elementary School in Connecticut, some opposed to gun control have suggested arming teachers. Critics say it's inappropriate or unworkable, but hundreds of school districts in at least 10 states across the country, most of them small and rural, already allow the practice, according to an analysis by the Education Commission of the States.

Sidney, Ohio

Sidney, Ohio, is one example. Dozens of guns are stashed in biometric safes in the district's seven buildings. "The district spent about $70,000 on safes, bulletproof vests, cameras, guns, radios and ammunition. Uniformed, armed officers cost $200,000 a year, and an insurance policy of $100,000 a year includes coverage for its staff with access to firearms. Those are negligible costs for a school district with a $36 million budget, the superintendent said," Erica Green and Manny Fernandez report for The New York Times. Every classroom also has a panic button, every school has a uniformed, armed guard, and metal detectors and a bulletproof window at the front entrance. School Supt. John Scheu told Green and Fernandez: "We can’t stop an active shooter, but we can minimize the carnage."

More than 100 public school districts in Texas have allowed teachers and administrators to carry firearms for more than a decade. Interested staff members must undergo specialized training and receive prior approval to either carry a concealed weapon or store one nearby. Gun-rights advocates say no mishaps or accidents have happened, and the state's program could serve as a model.