When students went back to school last week at Permian High in Odessa, Texas, they wondered what had happened to the place over the summer. Gone was their old wide-open campus, now surrounded by a security fence with controlled entry points and clusters of surveillance cameras. Inside the school, they had to wear bar-coded photo-ID badges, and in many classrooms, “black boxes” with mirrored eyes stared implacably down from the walls, above signs that read, IT SHOULD BE ASSUMED THERE IS A CAMERA INSIDE THIS ENCLOSURE RECORDING VIDEO AND AUDIO. What had happened was that Permian, like thousands of other schools alarmed by recent campus shootings, had responded by clamping down on all sorts of security problems, from fights to theft, vandalism, graffiti and intruders. In an approach not unlike urban police clampdowns of recent years, schools have tried to create a new environment of conspicuous order and security. What school administrators, parents and students worry about most are potential copycat gun crimes, especially after it was revealed last week that T.J. Solomon, 15, accused of shooting six classmates last May in Conyers, Ga., had referred to the Littleton, Colo., shootings in a note left under his bed. And last week’s armed assault on a suburban day-care center in Los Angeles only heightened the sense that every place is vulnerable. As a result, students returning last week to Allen High School in suburban Dallas found four new permanent, airport-style metal detectors and a sign that reads WELCOME TO ALLEN HIGH SCHOOL. UPON ENTERING THESE PREMISES ALL CARRY-IN ITEMS ARE SUBJECT TO SEARCH. In Orange County, Fla., students who wanted lockers or parking permits for their cars had to sign a waiver agreeing to random searches of both and stating that they “waive any expectation of privacy.” Instead of an old-fashioned fire drill, a high school in Williams Bay, Wis., carried out an extraordinarily dramatic exercise in the hope of showing students, teachers, police and paramedics what to do in case student gunmen storm the school: explorer scouts, dressed in camouflage and carrying rifles loaded with blanks, pretended to shoot the principal and take hostages. Few schools, though, have tightened their security as thoroughly as Permian High. It has formed an alliance with Sandia Labs, based in Albuquerque, N.M., which has three decades of experience in locking down top-secret facilities that manufacture, transport and store nuclear weapons. Sandia started advising schools on security in 1991 after Congress ordered the labs to share the wealth of its technologies. Yet protecting a nuclear facility, says Sandia analyst Mary Green, is in some ways easier than securing a school. “Nuclear weapons usually stay where you put them,” she says. “They don’t have a lot of civil rights, and they rarely stick six of their friends into their Camaro to go eat lunch at Taco Bell.”