Administrators and students at private schools tend to see their schools as safer than public schools. Spurred in part by the terrorist attacks of Sept. 11, 2001, many private schools have joined the national push to revamp campus safety plans. Kenneth S. Trump, the president of the Cleveland-based National School Safety and Security Services, applauds private schools for increasingly recognizing they could be targets of outside attacks, but faults them as playing down possible harm to students from internal threats as well. While consulting on crisis planning at some private schools, Mr. Trump said, he has found that school officials' perception that their schools' culture keeps students safe is an obstacle to carrying out basic security procedures. Such precautions include requiring all school visitors to sign in and providing adult supervision when students leave school at the end of the day, he said. In addition, private schools tend not to practice safety procedures, Mr. Trump said. Private school administrators say they worry much more about possible external threats than internal ones. School security experts say that Jewish schools have probably done more than many other kinds of private schools to address the possibility of outside threats of violence.