Teacher Lori Mackey was close to tears recently when she watched her five-year-old daughter in a crisis drill at her kindergarten doing “duck-and-cover” exercises.

Seven years ago Mackey witnessed the worst school shooting in US history. A 25-year-old drifter named Patrick Purdy killed five children and wounded 29 others, as well as one teacher, in the small Californian town of Stockton. Armed with an AK47 rifle he sprayed the playground of Cleveland elementary school with bullets. Purdy’s victims were all aged between five and nine and Cleveland’s teachers and children are still psychologically scarred.

Since then educators across the country have dusted off their crisis response plans. In the past three years, school-associated violence has claimed 150 lives. “We have gone from fist-fights to gun-fights, from fire drills to crisis drills,” said Ronald Stephens, director of California’s National School Safety Centre, which compiled the figures.

He estimates that all but about 10 of the deaths were caused by firearms or knives belonging to pupils or teachers - not evil madmen. “The greatest threat is the students and staff who come to that school every day,” he said.

Los Angeles Figueroa Street elementary school, where teacher Alfredo Perez was hit in the head by a stray bullet in February, this month installed bullet-proof glass in its ground-floor windows. In Washington DC, some inner-city schools have reportedly locked fire doors to keep intruders out.

But violence can strike without warning in the most remote areas. In Cokeville, Wyoming, population 500, a couple took an entire school hostage in 1986, including a woman delivering a parcel and a teacher who came to apply for a job.

Using a crisis plan schools can assign roles, lay down a chain of command, even set up a command centre. They can specify a site for the media, or even just a media spokesman. This week, Cleveland elementary school in Stockton was deluged with reporters seeking comment on the Dunblane massacre in Scotland.

“We can’t build fortresses around our schools because you can’t protect for everything,” Dr Stephens said. But a number are developing comprehensive and systematic safe school plans, he said. Some involve controlling site access for both vehicles and pedestrians. Entry and exit points are limited and visitors are screened.

The worst-hit urban schools have encouraged police and probation workers to set up sub-stations on the premises, and others have hired off-duty policemen and organised security patrols. But even signs saying all visitors must report to the office can help, he said. “You at least create a climate that says this campus is watched, controlled, and if you do not have a visitor’s pass we are going to challenge and remove you.”

At Stockton it took a long time before people felt safe going back on campus, said Lori Mackey. Initially, there were people who wanted 8ft walls and barbed wire. But teachers settled for carrying walkie-talkies in playgrounds and upgraded classroom intercoms, which were not all working when Purdy’s assault began.

Both victims and experts from US shootings stressed the need for long-term counselling after the initial flood of attention.

Wounded children who spend long months recovering can almost drop out of sight. Teachers in Stockton were expected to return to work almost immediately and ignore the sight of bullet-holes.

“What we learned from people who had experienced this type of trauma, is that they had a lot of recurring psychological problems,” said Rich Valentini, a teacher in Olivehurst, north of Stockton, when 20-year-old Eric Houston shot and killed three students and one teacher in 1992.

Lying in a room with dead and wounded students and teachers, Valentini turned over one of his students to give her medical help and found her face shot away.

“The best thing is for people to talk about it, to express how they feel, ” he said. “A lot of these kids need to be worked with even if it takes years. ”