At more than 100 high schools in Eastern Massachusetts, drug-sniffing dogs are brought in every year to search for everything from alcohol to marijuana.

In Quincy, video cameras follow students in the hallways while plainclothes security guards stay alert for drug activity. At Westford Academy, where students admitting in a survey to marijuana use jumped from 16 percent to 25 percent in the past decade, the principal decided to add a full-time police officer to the staff. Meanwhile at Newton North High School, counseling is considered the best way to reach students.

These days, schools are spending more time than ever trying to prevent teens from using drugs. While dog searches rarely result in major drug finds or arrests, law enforcement officials, such as Middlesex District Attorney Gerry Leone, said they are part of a prevention policy — one that includes communication, education, and surveillance – that is necessary to reach teens before they become addicted.

“In large measure, the canines are a deterrent,” said Leone, who believes increased cooperation between schools, police, state agencies, and parents is necessary to reduce drug use among students.

In addition, many schools now have a full-time police officer who bonds with students and tries to intervene before a student’s drug use gets out of hand. District attorneys also regularly come to schools to address students, and they bring along recovering addicts who talk about the dangers of drugs. Health classes discuss substance abuse and the effect drugs have on a teen’s body; school psychologists and counselors are on hand to deal with problems.

“There’s no magic bullet to this. It’s just a lot of rolling up the sleeves, and doing the hard work and getting the message out to kids to make good decisions,” said Essex District Attorney Jonathan Blodgett.

Even with all of these efforts, drugs and alcohol still can be found in and around schools. According to the latest state statistics compiled in 2011, 40 percent of high school students responding to surveys reported drinking every month, and 22 percent said they binge drink (consume five or more drinks within two hours). Also, 28 percent of teens said they use marijuana at least once a month, and 27 percent said they have been offered or sold an illegal drug on school property within the past year.

Six percent reported nonmedical use of a prescription drug in the last month, and another 5 percent said they had used an inhalant in the last month.

Blodgett and other district attorneys and educators said marijuana has steadily become more popular among teens since the law was eased in 2009, no longer penalizing possession of small amounts of marijuana with jail time. The law now calls for a fine for those found in possession of an ounce or less.

“I really believe the decriminalization of marijuana sent the wrong message to kids. It said you can get away with it, and I believe it is a gateway drug,” said James Antonelli, principal of Westford Academy, a public school. “The use of marijuana in this adolescent community is pervasive.”

Antonelli said he opposed the decriminalization, and earlier this year he initiated a bill filed by state Representative James Arciero that called for a $1,000 fine and a loss of a driver’s license for youths caught in a car with any amount of marijuana.

While that bill found little support on Beacon Hill, Antonelli has had stronger backing closer to home. Noting that admitted marijuana use had jumped among Westford Academy students in the past decade, the town held a forum on drugs in the spring.

In August, Antonelli — who calls in dogs to search the school several times a year — said he planned to add a full-time police officer to the school staff.

“It’s going to open a new line of communication,” said Antonelli. “Kids will come down and talk to the person and indicate a potential party of drug activity. A lot of kids don’t want to see it around the building, and they need a conduit to talk to somebody.”

Herb Levine, executive director of the New England Association of School Superintendents, said he thinks schools need to go one step farther and implement random mandatory drug testing.

“Drugs are everywhere — in the smaller schools, rich towns, poor towns, urban, and suburban. If you want it, it’s there,” said Levine, a former superintendent in Salem and interim superintendent in Peabody. He now serves as a special adviser to the Peabody mayor and school district.