At 7:50 a.m., yesterday, Montgomery County police undercover narcotics officers were making their daily checks on the school grounds at Bethesda-Chevy Chase High School, where according to one officer, drug use is "pretty much out in the open."

There, in front of the school, they observed a teen-age boy passing some marijuana to a young girl. Both youths, 15-year-olds, were arrested on the spot. Police charged one with distributing marijuana, the other with possessing marijuana.

At lunchtime police again saw some youths with marijuana in front of the school on a grassy area facing East-West Highway. "We didn't have enough manpower to clear out the whole school yard," said Officer Randy Crittenden, an arresting officer, so police approached and arrested five students they said they observed with marijuana. The students were over seated on a bench in front of the school.

All five youths - four 16-year-olds and one 15-year-old - were charged with possession of marijuana, police said.

As these noontime arrests were made, a crowd of students gathered on the school lawn shouting at police. Police then arrested at least one of the student protestors, charging the youth with obstructing a police officer.

Word of the arrests then spread quickly among the school's 1,400 students, along with charges - made by some of the students who were on the scene - that police had used undue force when making their arrests.

Shortly after the noon incident, a number of students walked into the street in front of the school and, for a short time, blocked traffic, according to police. At the same time, another group of students walked a few blocks to the Bethesda police station and "milled around outside," as their schoolmates were processed inside.

Students interviewed at the school yesterday said that, after the protest at the police station, about 30 students returned to school and held a brief sit-in on the school lawn.

"A lot of those students couldn't see why students should get arrested for getting high in the first place," said 17-year-old Laura Schisgall, a student at B.-C.C. "Other students more rational ones, didn't think students should be banged around by police or arrested when they weren't even smoking."

Schisgall, who witnessed the arrest, said police grabbed one student and "rammed him against a car" before arresting him.

Another student who asked not to be identified said she thought it was "silly" that police arrested students for smoking marijuana. "Don't they have better things to do? she said.

County police have been keeping an eye on all county schools since the school year began, according to Chief Robert J. diGrazia, in an effort to curb drug use by students during school hours. "We're looking at all the school grounds . . at some schools it's (drug use) carte blanche."

According to Capt. Ralph Robertson, who heads the Bethesda station, police have been looking into drug use at Bethesda-Chevy Chase since last spring. He said use of marijuana and PCP is common there and one student became ill on the school's front lawn last spring after overdosing on PCP.

"All you have to do is ride down East-West highway and you can see kids smoking dope" at the school, Robertson said.

Last year the school newspaper the "Tattler," attempted to investigate the depth of the drug problem at the school and assigned a student reporter to try to arrange drug deals. The newspaper reported that the student was able to arrange to buy $75 worth of marijuana and cocaine within four hours.

Yesterday, Thornton Lauriat, principal of the school, said he did not know in advance that police were going to arrest students. However, Lauriat said he did cooperate with police last spring, when they arrested two students for possession of marijuana.

"Last year, we called the authorities and asked for their help in dealing with the problem," Lauriat said. "But I wasn't informed in advance this time.

"I don't think drugs are any more or less a problem here than in any other high school," he said. "Our high school just has more visibility than other high schools because of its location and because several years ago this school got the reputation as having a drug culture. That past image may still be hanging around."