"We don't have money for a security guard, but this is a better solution," Superintendent David Thweatt said. "A shooter could take out a guard or officer with a visible, holstered weapon, but our teachers have master's degrees, are older and have had extensive training. And their guns are hidden. We can protect our children."
The article says that Oklahoma is also working legislation to allow teachers to carry.
Finally - some common sense.
Texas town allows teachers to carry concealed guns - Yahoo! News