Social studies teacher Leroy Swain usually arrived at McKinley early, about 7:30 a.m., in plenty of time for his 8 a.m. government class. But one winter morning, his black-and-orange taxicab -- which he uses to earn extra income after school and on weekends -- was nowhere to be seen in the school parking lot.

A few minutes before 8, a car pulled into the parking lot. Out jumped Swain, whose cab had broken down on the way to work, forcing him to find another way to work. Swain raced across the parking lot, sprinted up the two flights of stairs and arrived for his class in Room 315 just as the bell rang.

This was typical of Leroy Swain, a teacher whose dedication to his job stands out in a school where some students -- and even a few teachers -- have a casual attitude toward getting to class on time. Swain has little patience for tardiness; when several students in his second-semester government class had trouble getting there by 8 a.m., he told them to transfer to a later class. It was his way, he said later, "to shake the fat out."

He is just as aggressive about getting his students to participate. Trying to spark some discussion among the 23 students present one Friday morning in early February, he asked someone to list the various forms of government. A boy sitting in the corner timidly raised his hand, holding it slightly above his shoulder. Swain walked over to the boy's desk and gently grabbed the boy's arm. "When you raise your hand, I want you to reach for the sky," he said, demonstrating. "I want people to see who you are."

Swain is part disciplinarian, part cheerleader. His students comment on his willingness to listen, his persistence in asking for their opinion, his open manner. Almost every day, students came to his classroom before school started to talk to him about a family or school problem.

His style has worked particularly well in his "dynamics of relationships" class, a new course taught at McKinley for the first time last year. It is a kind of crisis prevention course that covers a wide range of issues confronting today's teen-agers: sexuality, suicide, how to talk with a parent, the importance of friendship. "In here, we can talk freely," said Brigette Moore, the senior class president last year.

Swain's class was so popular that students occasionally cut other classes to attend. Although Swain did not want to encourage any rule-breaking, he let them stay if he thought they had a personal problem that had to be dealt with immediately.

The discussions often turned into free-flowing exchanges on morality and values. Principal Bettye W. Topps was impressed with the way he handled the class, often bringing visitors from other school systems to observe.

One day last December, he asked the students if they had shared with their parents some tips found in the textbook on how to improve communication between parents and teen-agers. No one had.

"Mr. Swain, you act like you're trying to solve every problem with this book," said one girl, who had previously described her stormy relationship with her mother. "Everybody can't solve their problems with this book."

Swain suggested that the book was the means to an end -- the way to open up a difficult conversation. "I would appreciate it if you would show those 12 tips . . . to your parents tonight. This could be a start."

He often drew on his own experiences in talking to his students. A D.C. native, he graduated from Roosevelt High School in 1966 and ended up in D.C. Teachers' College only because, he told his class, the father of his then-girlfriend insisted that if he planned on dating his daughter, he had better enroll in "somebody's college."

He often runs into his students after school, while driving his cab through neighborhoods in Northeast and Southeast Washington, where he prefers to look for customers. One hot Friday night in July, several weeks after the end of the school year, I rode with Swain as he drove his cab through the streets of Southeast.

It was a night to reflect on issues large and small, on how the year had gone and on the state of education in today's urban high school. He picked up a young man in gray shorts and T-shirt near the corner of Alabama Avenue and Stanton Road, where a crowd of more than 50 men and women gathered along a sidewalk leading to an apartment building. Swain asked the man why the crowd had gathered. "That's where they sell nar-co-tics," the man said matter-of-factly.

That led Swain to a discussion of the lure of drugs for some teen-agers. "Deep down these kids aren't bad," he said. "They want to do right. But there's no incentive to do it. They can sell drugs. Hang on the corners. Socialize. Wear the finest clothes and make easy money. Nobody bothers them. It's a good life."

Swain said he fears that life for these kids "is over," that they will not rise beyond where they are now if the school system doesn't acknowledge the extent of the problem and get tougher on both teachers and students. "The system should step in with some firmness," he said. "If you come down hard, the results will be well-known."

It was time, he said, to stop graduating youngsters who aren't prepared, even if that meant failing a significant number of students. He paused, reflecting on the impact of what he was proposing. "You don't know how much the system could stand," he said. "That might be the most difficult part." But he said there was no choice. "You can't back off," he said. "It's going to take time."