JERUSALEM – Americans intent on ensuring a school massacre like the one in Newtown, Conn., never happens again could learn a lot from Israel, where the long menu of precautions includes armed teachers. The Jewish state, which has long faced threats of terrorist strikes in crowded locations including schools, takes an all-of-the-above approach to safety in the classroom. Fences, metal detectors and armed private guards are part of a strategy overseen by the country’s national police. And the idea of armed teachers in the classroom, which stirred much controversy in the wake of the U.S. attack, has long been in...