Some Massachusetts educators had new subjects to discuss this school year. And they weren’t talking only about academics. They were discussing blast waves and incendiary devices, courtesy of a forum titled “Explosives In Our Schools.”

The morning-long seminar, held in late August, examined explosives ranging from small firecrackers to large military missiles, as well as internet bomb-making instructions. Officials admitted the chances are remote that any educator will encounter a bomb during a school day.

But the mere possibility—combined with the more likely scenario of a student smuggling old military gear or explosives swiped from construction sites into classrooms to show friends—proves it’s necessary to educate teachers about them, said Trooper Tim Murray of the Massachusetts State Police Bomb Squad.

“From September to June, you guys are in the trenches right there with us,” Murray told nearly 200 administrators and law enforcement officers assembled in a library at Merrimack College in North Andover.

He displayed a wide range of explosives and warned about potential bomb ingredients that can be found in the chemistry lab or janitor’s closet of most schools.

Many bomb ingredients—such as gunpowder, small motors, wicks, fuels, and other tools—can be bought legally at hobby shops, but Murray warned teachers not to dismiss them as harmless.

“It’s bells and whistles that should be going off,” he said. “Is this kid really into model rocketry? Or is he in the beginning stages of constructing explosives?”

Essex County District Attorney Kevin Burke, who hosted the event, said the training was necessary in a “post-Columbine” world, referring to the two teens who killed 12 students, a teacher, and themselves in April at Columbine High School in Littleton, Colo.

The two gunmen also planted and set off numerous bombs during their siege.

In the wake of the massacre, approximately 75 eMail and telephone threats were reported in Essex County schools, resulting in about a dozen evacuations, Burke said.

“Anxiety levels were so high, and significant numbers of kids stayed home from school,” he said. “It’s not about seeing kids as enemies. It’s about having the ability to deal with threats and scares.”

Educators were also told to evacuate their students if a bomb is discovered.

“Don’t do a John Wayne … Don’t touch,” said Murray. “Move the people away from the threat. Don’t move the threat away from the people.”

Some administrators said they’d had close calls with explosives in the past.

“Kids, especially the brighter ones, think this is ‘cool’ because it involves a little bit of chemistry and electricity,” said John Ziergiebel, assistant principal at O’Maley Middle School in Gloucester.

Several years ago, Ziergiebel said, a seventh-grader was discovered with the makings of a rudimentary bomb—including fuse and gunpowder—apparently brought in to impress bullying classmates.

But as a new administrator, Ziergiebel said, he seriously underestimated the danger the device posed.

“I didn’t know not to touch it,” he said. “A custodian picked it up and my boss took it apart. We’d never do that again.”

Kevin Lyons, director of student services for Haverhill schools, said it’s important to balance safety training with programs on how to reach disturbed kids before they begin dabbling in weaponry.

“We don’t want to create a level of paranoia,” he said. “It’s the disconnected kids who get into the nasty business and it’s (just as important) that we get the same emphasis on prevention.”