Nearly 30 students from Palm Beach County high schools were nabbed in an undercover drug sting last week and arrested for selling marijuana near school campuses.

Since the fall, undercover officers from the school district Police Department have posed as students at Park Vista, Royal Palm Beach and Jupiter high schools.

As part of “Operation D-Minus,” the officers attended classes for most of the school year and even did homework assignments. They also made the drug buys.

On May 2 and 3, police went went into classrooms to arrest some of the students. Others were arrested at their homes. A total of 23 students were charged with sale of marijuana within 1,000 feet of a school, including a few from William T. Dwyer High School and one who is home schooled.

Two 11th graders from Jupiter High School were arrested on other drug dealing charges.

All will be charged as adults, officials said. The oldest among those charged is 20, and a student in Jupiter High’s adult-education program.

The investigation also led to the arrest of two middle school students, ages 13 and 14, charged with burglary. One goes to Independence Middle School and the other is home schooled.

The last undercover drug sting in the schools was Operation Schoolhouse in the 2005-2006 school year.

“We do these [operations] because we know there are drugs in schools, and we’re going to keep doing them,” Superintendent Bill Malone said. “I doubt I will live long enough [to see] the time that it’s not necessary to do these.”

Active investigations continue on those campuses, schools Police Chief Jim Kelly said. Similar operations are planned at others schools, but he declined to identify them.

“I think they should be looking over their shoulder,” Kelly said of other suspected drug dealers.

Moreover, parents should be aware of what their children are doing, he said.

Current high school students might not remember drug busts five years ago, Malone said, but “I guarantee that they will remember this one next year and the year after.”

School District policy requires the students to be expelled when caught selling drugs. Those arrested have the option to continue with alternative schooling, either online or at alternative teaching centers.