The good sense of American young people appears to be reasserting itself. The latest national survey of drug abuse among high school seniors lends weight to previous reports of decline or leveling off on almost every count. Most striking was the drop in daily marijuana users, from one out of nine seniors in 1978 to one out of 14 last spring. There also was less usage of other illicit drugs, less cigarette smoking, and at least no increase in the 6 percent using alcohol daily. Furthermore, those who did use drugs said they were tending to use them less. And there was a rise in negative attitudes toward drugs, exemplified by a higher percentage seeing great risk of harm in regular use of marijuana and a lower percentage favoring legalization of marijuana.
Kudos not only to the young people opting out of the drug culture but to the parental, religious, educational, governmental, and media efforts at prevention.
But how far the United States still has to go may be shown in several ways:
* Despite the ''tangible'' improvements, the survey found America's remaining levels of drug abuse among young people higher than in probably any other industrialized country.
* The students said drugs were as available and affordable as ever. The challenge to enforcement of drug control laws is plain.
* According to other reports, the decline in student drug use has been accompanied by older-generation use to the point of causing such effects as what New York authorities call a serious drug problem in the Wall Street area. Also New York drug counselors have noted that a major impediment to preventing teen-age drug abuse has arisen in the number of parents who themselves use drugs. The toleration of youthful drinking by drinking parents has always been a problem. Now it is the toleration of marijuana by parents who use it or used it in their own younger days.
* Fundamentally insidious is the growth among young Americans of the notion that illicit drugs have joined the commonplaces of life. A New York Times survey last year found this to be the nearly universal attitude among teen-agers in the New York metropolitan region. The indication was that, through media images and daily experience, today's young people have become more immersed in the drug culture - and at a younger age - than any before them.
Whatever the decline in the use of illicit drugs, a moral decline will have taken place in America if they become entrenched as an accepted commonplace in the American scene. The rise in negative attitudes toward drugs has to be reinforced and built upon. A rise in positive attitudes toward enjoying life, meeting its challenges, overcoming its disappointments - without illicit stimulation or escape - has to be encouraged. For all the admirable efforts by others, families must see that the primary responsibility is theirs.