If an armed intruder breaks into a classroom in rural Pennsylvania’s Blue Mountain district, he “will face classroom full of students armed with rocks,” Superintendent David Helsel told state lawmakers. Every classroom has a five-gallon bucket of river stones. Students have been told to defend themselves, if necessary. The idea of kids fighting a gunman with rocks has met with mockery. Cheryl Magness, writing in The Federalist, thinks preparing students to defend themselves i