After a series of high-profile shootings since the late 1980s, US school districts have stationed police officers on campuses, established single points of entry for buildings, trained staff through "lockdown drills" to minimise casualties and promoted programs to teach conflict resolution and fight bullying.
In the 2009-2010 year, 17 children ages 5 to 18 died in homicides at US schools, travelling to or from campuses or at school events, according to the US Education Department. That's about half the annual figure during much of the 1990s. In a population of more than 50 million students, the school-related death toll has been about 1 per cent of all homicides for that age group.
"Schools are safe, and they are safer than they were," said Stephen Brock, a professor of school psychology at California State University, Sacramento, who has trained more than 4000 educators in preventing and responding to such crises. "Unless we turn our schools into prisons, we aren't going to be able to prevent some truly motivated person from entering school grounds. There are things we should do, but there are limits."
The latest school shooting, in Newtown, Conneticut, left 20 children dead, despite lockdown and security measures.
Two previous killings, in particular, led to the current round of safety measures in public schools. At Columbine High School in Littleton, Colo., two students in 1999 killed 12 classmates and a teacher. At Cleveland Elementary School in Stockton, Calif., a gunman in 1989 murdered five students.
Today, security often varies based on the age of schools, as newer buildings typically have the most important protection - a single entryway, often with a vestibule or buzzer to control access - according to Paul Timm, president of RETA Security Inc., which consults with school districts.
Middle schools and high schools often station a police officer on their campus, both for security and to train staff and form relationships with students to prevent violence, said Mo Canady, executive director of the National Association of School Resource Officers in Hoover, Ala. Such full-time officers are less common in elementary schools.
"We do see that as a gap," Canady said in a telephone interview. "It is a funding issue.'
Though some schools have tried metal detectors, most have found the technology expensive, unnecessary and difficult to staff, security experts said.
Hamilton High School in Chandler, Ariz., has eight security guards on its fenced-in campus of 3600 students, along with a system of guest passes.
Still, the school doesn't subject everyone to searches with metal detectors, as they do at airports, an approach that would be unworkable, said Richard Baniszewski, Hamilton's assistant principal.
"Our school district takes security very seriously and provides resources for it," Baniszewski said in a telephone interview. Still, "it's not a perfect system," he said.
After Columbine, school districts have increasingly focused on what Brock calls "psychological security," or measures that foster communication among staff, parents and students.
The programs stress clear rules about speaking respectfully, walking in the halls, raising hands - as a way to promote an environment that discourages violence. School counselors also work with students on anger management and anti- bullying messages.
The goal: Make sure troubled children get help, preventing them from turning to violence.
The shooting at Sandy Hook Elementary School in Connecticut illustrates the limits of these measures. The school locked its entrances and controlled entry through a buzzer system and its staff seemed to follow a lockdown plan, which included securing kids in classrooms and hiding them from sight, according to initial reports.
The heavily armed, 20-year-old gunman, Adam Lanza, forced his way in, authorities said. He shot through glass to enter, said Maryann Jacob, an assistant librarian. He also killed six adults and himself.
Parker Whitney Elementary School in Rocklin, Calif., demonstrates the challenge of providing security on often open U.S. school campuses.
It isn't a single building with an entrance that can be closed. Instead, it's a campus, almost like a strip mall, with buildings and six stand-alone classrooms that don't interconnect.
Students must walk outside to move between rooms and use the bathroom. Access isn't limited to a single locked door. Visitors are required to obtain passes, and all employees must wear ID badges.
Like many schools, Parker Whitney focuses on its response to a crisis - through repeated practice that is a far cry from the days of the Cold War when students were told to hide under desks in the event of a nuclear attack.
The fire drill, practiced monthly, is "the screaming cricket," with a high-pitch chirping noise, said Denny Rush, principal of the 450-student kindergarten-to-sixth-grade school, about 20 miles northeast of Sacramento.
"Lockdown" sounds more like an ambulance wail, and students practice four times a year, twice in the classroom and twice while at recess.
During such exercises, doors to classrooms are locked, students shuttle under their desks, lights are turned out, and curtains are closed. Student learn "duck and cover."
In 2010, when a gunman fired shots in a mall a few miles away, the school carried out lockdown for real. In no situation have students been in danger, Rush said.
Some schools take no chance with visitors.
"There is only one way in, through the main office," said Joseph Martinez, principal of Carpenter Community Charter School in Studio City, CaliF. "We take down their IDs, they have to sign in. If it's not an employee, they are clearly labeled with a sticker. We have security cameras at our gates."
At Devonshire Elementary School, in the Chicago suburb of Skokie, Ill., all the doors are locked. Visitors buzz in. They are asked for identification, which is screened through a machine transmitting data that can perform a background check, said Randy Needlman, who has been principal for 11 years.
In South Hadley, Mass., Plains Elementary School has had a special challenge: securing an 80-year-old red brick building with 25 doors, at the intersection of two highways.
Until seven years ago, parents walked in the front door to the center of the building to check in at the main office, said Jillayne Flanders, its principal. To improve security, the school relocated the receptionist to the front door, she said.
When Flanders visits schools, she is struck that many don't take those precautions, partly because they are so focused on creating an environment that welcomes families.
"A lot of schools trust that nothing as horrible as what happened in Connecticut is going to happen to them," Flanders said in a telephone interview. "They want to have a warm and welcoming school community - to be safe but not have people come into a jail."
- Washington Post