For the first time, they're also checking the county's middle schools in an effort to nip any potential problems in the bud, said William B. McKinley, director of secondary education.
"We'd be foolish if we had a resource such as this and didn't use it to the fullest extent that we could," McKinley said.
Because students have no way of knowing when the dogs will be at a school, the scans are expected to act as a deterrent, McKinley said.
But the dogs also can help school officials find out which students are using drugs so the problem can be dealt with, he said.
County high schools were subject to the random visits - courtesy of the Maryland State Police - from 1986 until the 1995-96 school year, when the police agency discontinued the program, said Martha Roulette, director of student services.
The Sheriff's Department and city police took up the ball last month at the request of Schools Superintendent Wayne F. Gersen, Roulette said.
Hagerstown Police K-9 Officer Mike King said all three of the departments' drug-trained dogs will be used on each visit.
Three schools - South Hagerstown High School, Williamsport High School and the Alternative School - were scanned in the first wave of visits on Feb. 27.
Students are kept in their classrooms while dogs check out the locker areas and parking lots, King said.
Police tell school administrators if a dog "alerts" to an area where drugs might be, he said. It's up to school officials to conduct a search and take the action they feel is appropriate.
School system officials said no drugs were found as a result of the scans.
That's not surprising, said Clear Spring Middle School Principal James Conrad, who is familiar with the K-9 visits from the time he was principal of North Hagerstown High School.
"We don't expect to find very much. It's more preventative medicine really," Conrad said.
The visits demonstrate a solidarity between the schools and police on the issue of drugs, said E. Russell Hicks Middle School Principal Ralph L. Kline.
"It's nice that the community sees that the schools and law enforcement are working hand-in-hand," Kline said.
South Hagerstown High School students have mixed opinions about having the dogs come into the schools.
Freshman William Matthews is all for it.
"I think that they should do it to keep drugs out of the school," said Matthews, 14. "People come to school to learn, not to do drugs."
Sophomore Kelli Jones questioned both the safety and effectiveness of the practice.
Jones, 16, said she's against having the parking lot scanned because it's an invasion of students' privacy.
Sophomore Erica Sprankle said she doesn't care if the dogs come or not.
"I don't have anything to hide," said Sprankle, 15.