Brian Berthiaume had never seen a kid with the discipline to do it. "Most kids can't quit cold turkey," said the director of Montgomery County's Phoenix School for kids with drug and alcohol problems.

The 18-year-old to whom he referred later sat in a living room talking about how he did it. In a landscape that is littered with failures and the more normal stop-start-stop-start road to getting straight, I had come to find out what motivated this young man to mean it when, on the first day he came to Phoenix after being thrown out of Wheaton High School, he looked Berthiaume in the eye and said he would stop then and there.

"When I got arrested at school," said the young man, "that was the worst day in my life. I'm the first one ever to get in trouble through my whole family history. I told my mother I would stop and I did . . . . "

He had smoked marijuana two or three days a week, usually on weekends. The April l983 issue of the respected New England Journal of Medicine noted a dramatic increase in marijuana use among high school seniors during the past two decades: 59.5 per cent of the class of l981 reported having used the drug, and that is probably a conservative figure.

"Regular marijuana users . . . tend to place a lower value on academic achievement and a higher value on independence, as compared with nonusers," the Journal said. "Those who use marijuana regularly also have less motivation; perform more poorly in school; have fewer religious convictions and are more involved in antisocial and delinquent behavior, such as stealing, brawling, vandalism and truancy. As a group they possess personality traits indicative of maladjustment, including rebelliousness, depressed mood, and low self-esteem."

The young man said he smoked "for relaxation." The Journal said frequent users told researchers they smoked the drug primarily to "cope with feelings of stress, anger, depression, frustration, or boredom."

He was arrested at Wheaton and was charged with possession of marijuana with intent to distribute. He denied that he ever sold drugs and said the marijuana he had was for his own use. He was carried from school in handcuffs, later expelled and released in the custody of his mother. After his good record at Phoenix, the charges later were dropped.

This young man is the eldest of a family of five children that immigrated from Jamaica two years ago. The mother works as a nurse's aide and until the stepfather immigrated recently, the young man was the "man" of the family and carried the pride of and responsibility for the extended clan which included his grandmother.

At a meeting with Phoenix faculty and his mother, he wept in humiliation. At home, he barely spoke for weeks.

The boy's humiliation and feeling of having failed his family is a different attitude from that of most youths he sees, says Brian Berthiaume. "It is good he was so embarrassed and humiliated because it gave him the motivation to become drug-free," he said. "Most kids are not overly embarrassed about coming to school here. But his culture was a powerful stimulant. His humiliation provided the extra motivation to restore his dignity and regain his respect within the family. He wanted to shake the image of being a kid who was involved with drugs."

Phoenix School was set up by Montgomery County officials several years ago as one of several ways to stem the spiraling incidence of drug use among younger and younger kids there. "Everybody was trying to help each other in staying straight," said the young man. School policy required frequent urinalysis to determine which students slipped and did not remain drug-free.

This young man has been playing bass in a reggae ensemble with several friends, and I asked him if he was fearful of being tempted to return to drugs.

"It's ignorance and stereotyping that all musicians use drugs. An individual is an individual," he says. His ambition is to enter the Diesel Institute of America and to continue playing music for enjoyment.

Berthiaume thinks this story had a happier ending than most because of his strong motivation to flee the debilitating behavior produced by substance abuse. "I think he is on the right track," he says. The young man later proves that reading right. "I don't want to bring any more shame on my family," he vows.