When high school senior Bill Bryan announced that alcohol would no longer be sold at the dances he organizes to earn money, some friends predicted a nose dive in attendance.
They were right -- but only once. At the second no-alcohol dance, student attendance picked up so much that Bill is looking for a larger facility in Gwinnett County (near Atlanta) for his next dance.
When a small group of students at Westmont High School in Campbell, Calif., began holding a series of drug-free social activities, a popular football player , among others, joined in.
No one is quite sure why the latest national data show a continuing decline in marijuana use and a leveling off in alcohol use among high school seniors. But experts on drug abuse give substantial credit to growing student awareness of the health effects of marijuana and a willingness among some youths to stand up and say, in the words of Karen, a Westmont student:
''We're the people who don't want to get drunk, who don't want to get stoned.''
The number of high school seniors using marijuana on a daily basis has dropped steadily from 10.7 percent in 1978 to 9.1 percent in 1980 - then to 7.0 percent in 1981, according to the University of Michigan's annual survey.
The 2 percent decline last year, following three other years of slight decline, is the strongest evidence yet of a true downward trend.
Parents and drug-abuse experts express mixed views on the effect of a recent report by the National Academy of Sciences on marijuana. Some say the report, which left a number of long-range health effect questions open, will be used by some to play down the dangers of marijuana use. Others say that because the report raises so many questions it may discourage some potential or actual users.
The report, the result of 15 months of reviewing published information on marijuana, concluded: ''The scientific evidence published to date indicates that marijuana has a broad range of psychological and biological effects, some of which, at least under certain conditions, are harmful to human health. Unfortunately, the available information does not tell us how serious this risk may be.''
But the report added that what is known of the health effects of marijuana ''justifies serious national concern.''
Rosellen Amisano, a mother active in drug prevention programs in the Atlanta area, says she was ''terribly unhappy with the soft line'' the report took. She worries some youths will see its lack of precise conclusions as a justification for further use.
But Robert DuPont, former director of the National Institute on Drug Abuse, sees the report less as a ''green light'' than a muddying of the waters on marijuana effects. ''At least they recognized it as a problem,'' he said in an interview here during a recent national drug abuse conference.
Lee Dogoloff, executive director of the American Council on Marijuana and Other Psychoactive Drugs, says the downward trend in marijuana use stems from growing awareness by youth of what they ''see it doing to other kids.'' ''Kids know they can't learn when they're stoned,'' he says.
The University of Michigan survey of the class of 1981 found an increase from 35 to 58 percent in the past year in youth who see a ''great risk'' in regular use of marijuana.
And 75 percent say their close friends would strongly disapprove if they regularly used marijuana, an increase from 69 percent a year ago.
The survey also found use of alcohol fairly level since 1977, little change in use of cocaine, barbiturates, LSD, and heroin. Cigarette smoking continued to decline, though 13.5 percent smoke at least a half pack a day. There was an increase in use of stimulants and methaqualone.