Last school year a band of plainclothes police officers periodically would stroll up a grassy knoll, known appropriately as "The Hill," outside Bethesda's Walt Whitman High School and arrest some of the youths who made a habit of smoking marijuana there.

When school opened this year, however, "The Hill" was gone -- rendered into a gaping hole where the school's new auditorium some day will stand. Gone, too, at least for the foreseeable future, are the controversial drug raids Montgomery County police launched last year at the county's senior and junior high schools.

Although it is too early to gauge the level of marijuana use by students this year, police and school officials say they are confident that new drug control programs and improved communications among the police, educators and students could make it unnecessary for a repeat of last year's campaign in which more than 330 students were arrested in 79 raids.

"The police are not going to restore the raids but, if they feel or school people feel the situation is out of hand, they will take whatever selective measures that are necessary," said Kenneth K. Muir, a spokesman for the county school administration. "That's not to say we're going to ignore drug abuse, but we've got to keep a balance and focus on education."

Although last year's crackdown enjoyed widespread community approval, it was criticized by some as a political gambit by former Police Chief Robert J. diGrazia to counter the unfavorable reputation he had gained within his department as a liberal innovator. The popularity of the drug busts notwithstanding, diGrazia was fired Dec. 5 of last year.

The raids also sparked student protests at several high schools, including Whitman, where police officers were pelted with a hail of stones and milk cartons by angry students.

Marion Greenblatt, the new president of the county school board, said she hopes that all that is a thing of the past.

The school system, she said, has begun a new four-point program to combat drug-abuse that includes a health education course for ninth graders, the Phoenix School in Silver Spring for students with serious drug problems, an expanded role for hallway monitors in the schools, and a soon-to-be-completed report from a community task force organized after last year's busts.

"Drug abuse is a very serious problem and these four points are just the beginning," said Greenblatt. "We still need a comprehensive plan. We have to make sure schools are not a haven for drugs and alcohol."

Greenblatt and several other school officials say the school system should not be forced to assume primary re- sponsibility for controlling the drug abuse problem, which they claim enters the school environment as a result of prevalent drug use in society. Said school spokesman Muir: "The major point of schools is to teach."

The effectiveness of last year's high-profile crackdown is debatable. Some students said their pot-smoking friends got high less frequently, at least in or near school, because they feared the raids. But that was not always the case.

"We expected the number of drug arrests to drop once kids came to the conclusion the police weren't kidding. It didn't," said Michael Michelson, an administrative assistant for student affairs in the school system. "Maybe some kids have been terrified to the point where they won't smoke a joint, but by and large the drug raids haven't reduced usage."

Indeed, although he had no hard statistics on the matter, Police Chief Bernard Crooke said drug use this year is still "a tremendous problem."

Less than half of the 330 students arrested during the organized raids were referred to juvenile court authorities, and only a small portion were taken to court. Many of those arrested were dispatched on community clean up parks, wash county cars, work in the libraries or day care centers or otherwise make amends. A small fraction of those arrested were deemed to have serious drug problems and were enrolled in treatment programs.

If nothing else, the raids of last year may have made drug use less visible. Over at Walt Whitman last week, one junior said: "The busts made a lot of people scared up on 'The Hill.' They just went other places."

Those in the know at Whitman say the pot smokers this fall have established a new hill for their extracurricular activity.

Only 11 of Whitman's 1,960 students were arrested in last fall's drug busts, but if the notoriety of a few diminishes the achievement of many, Principal Jerome Marco says that is "a cross you bear."

Marco points to such successes as the school's high rate of college acceptance and National Merit scholars. Drugs, nonetheless, are a fact of life.The student newspaper in a 1977 survey reported that 23 percent of the students there "got high" in school at least once a week.

For some students who smoked marijuana as juniors last year, the days of getting high are over. Said one senior at Whitman last week: "There were a lot of people stoned out of their brains last year. I used to get high, but I skipped too much. I got B's and C's. I should have done a lot better." This year, he said, he is going after the A's.