Drug use in Maryland high schools and junior high schools declined slightly over the last two years, but those students who are using drugs are using a wider variety, from marijuana to heroin, according to a new statewide survey.

The survey shows that in Montgomery County, drug use in 1982 declined significantly for high school students, but increased slightly for students in eighth grade, compared to 1980.

Drug use among Montgomery high schoolers was also less than for students statewide.

In Prince George's, exact figures were not yet available, but schools spokesman Brian J. Porter said, "We will show a decline in the self-reported use of drugs, generally below the Maryland averages."

A typical student reaction came from Steve Arslanian, 18, a senior at Bowie High, who said: "I guess it's blown out of proportion somewhat. It doesn't tell the whole story." Arlslanian said he felt that students tend to over-report their drug use on such a survey.

Maryland seniors use slightly more marijuana than students nationwide, the survey found, and they use twice as much cocaine and four times as much tranquilizers, quaaludes, barbiturates, PCP and heroin.

Officials cautioned, however, that the nationwide comparisons may be misleading, since the the total number of students using those harder drugs is fairly small.

These were the results of a survey conducted for the Maryland Drug Abuse Administration. The survey, taken last December, covered more than 46,000 students at 122 schools, in 18 of the state's 24 subdivisions.

Detailed results will be made public next week, but Montgomery officials made their portions available yesterday.

The survey found that 87 percent of high school seniors reported current alcohol use, with 27 percent reporting that they use alcohol frequently.

The figures for Montgomery were even higher, with 90 percent of seniors reporting that they use alcohol, 28.5 percent of them frequently.

Montgomery School Superintendent Edward Andrews, in a letter to school board members, wrote: "Maryland adolescents consume an alarming quantity of alcohol."

Andrews said that they averaged "the equivalent of two six-packs of beer per week."

In the area of drugs, 34 percent of Maryland's seniors reported using marijuana, 14 percent reported using amphetamines, and 10 percent said they used cocaine. Marijuana use is down from the 1980 survey, but use of amphetamines and cocaine shows increases.

Maryland eighth graders statewide similarly show less marijuana use: 14 percent in 1982, compared to 17 percent in 1980. Amphetamine use was up slightly in that age group, but the number of users at that age was too small to make this difference significant.

In Montgomery, drug use showed a decline from two years ago for the seniors, said Dr. Richard L. Towers, director of the schools' department of interagency, alternative and supplementary programs.

Towers pointed to figures showing that 29 percent of seniors used drugs in 1982, compared to 36 percent in 1980.

Among 10th graders, 19 percent reported using drugs in 1982, compared to 29 percent in 1980. Drug use among eighth graders showed a slight increase.

Towers attributed the decreases to stepped-up, new antidrug efforts, including placards on Ride-On buses, 50 parent-training groups, counseling sessions, and a new health curriculum.