Boonsboro Principal Helen Becker refused comment.
Wednesday's bomb threat was the second time since Monday that deputies responded to the school and charges were filed. It was the third incident at the school this week.
Across the Tri-State region at least 16 students were charged for bomb threats or related incidents since the April 20 massacre at Columbine High School in Littleton, Colo. In other cases charges are pending or were handled by school authorities.
Boonsboro's bomb threat was unrelated to a trespassing incident and suspicious package found at the school Tuesday, Cooper said.
On Tuesday around 8:30 a.m., deputies arrested Ethan Wayne McCoy, 18, of E. High St., Sharpsburg, and charged him with trespassing on school property and trespassing on private property.
Later that morning, more than 800 students were evacuated from Boonsboro High School for two hours when a teacher found a suspicious package that later proved to be harmless.
No charges were filed and the package was sent away for analysis, Cooper said.
Officers from the Maryland State Police, Hagerstown City Police and sheriff's deputies have been in county schools all week in response to a series of bomb threats and rumors following the Littleton, Colo., tragedy.
Most county schools experienced a drop in attendance on Monday when rumors spread that violence would occur.
None of Washington County's schools reported high absentee rates Wednesday, Director of Secondary Education Boyd Michael III said.
Boonsboro High School reported 7 percent of its students absent Wednesday, which is slightly higher than its normal rate, Michael said. North Hagerstown High School absentee rates dropped from 46 percent Monday to 12 percent Tuesday.
Aside from Boonsboro's bomb threat, there were no problems with violence. "Everything is quiet," Michael said Wednesday afternoon.
Deputy Cooper has spent the past week at Boonsboro High School, patrolling the grounds, talking and having lunch with students.
Prior to this week Boonsboro High School's three resident deputies would patrol the school's parking lot in the mornings and afternoons focusing on traffic control.
He said deputies will remain at Boonsboro High School until the end of the school year in June.
From talking with students, Cooper said he learned that they feel reassured having police in school.
"The kids are scared but things are going OK," he said.
Cooper said despite the three incidents this week, the atmosphere is reasonably calm.
"They want things back to normal and resume regular school activities," he said.