President Barack Obama's announcement last week of a wide-ranging anti-violence plan in response to the Newtown, Connecticut, school shootings comes as many districts are adopting new and sometimes dramatic measures--including arming teachers and volunteers--intended to prevent similar tragedies in their own schools. School safety experts warn against making major changes to security procedures without thinking through those changes. In many communities, however, people say not taking action after the deadliest K-12 shootings in American history is just not an option. Other school systems, municipalities, and law-enforcement agencies around the country are hiring more school resource officers, organizing armed volunteers to patrol schools, or ratcheting up training for educators and school guards on how to handle so-called active-shooter cases.