A soft tapping at the apartment door interrupted our interview. Charmaine Ford, 29, stopped telling me the story of how she became a teen-age mother, pulled back on the red metal door as far as the chain lock would allow and cautiously peered out into the hallway.

There stood one of Charmaine's neighbors, a 6-year-old girl, her cheeks stained with tears, her voice barely audible, her body so overcome by her crying that her braided pigtails shook. Charmaine quickly unlatched the door and tried to calm her. The girl managed to explain that she had been taking care of her 7-month-old sister since her mother had left early that morning. It was now 8:30 p.m.

Still crying, the girl said her mother had just telephoned, but only to say that she was spending the night out. Before hanging up, the mother told the girl to fix a bottle of formula for the baby. Confused by the call, unsure how to make the formula, the girl had panicked.

It was not the first time this had happened. Charmaine had often argued with the girl's mother, 23, about the safety of leaving the children home by themselves in an apartment on Condon Terrace SE, just two blocks from a street corner that police say is a dangerous drug market. But the arguments went nowhere; the woman always said the 6-year-old girl was "big enough" to care for herself and the baby. Now, the girl was standing in the hallway, her pretty cream-colored dress hopelessly wrinkled and her face contorted by her crying.

Charmaine took the girl back to her apartment to make the formula. Charmaine's mother, Rosalee Ford, who lives in Charmaine's apartment and had been listening to the little girl's story, turned to me and said: "Left that baby in there by herself . . . . Left that baby with no milk or nothing. I think it's a shame. These young girls having these babies."

This episode took place Oct. 4, 1984, two months after I rented a one-bedroom basement apartment in Washington Highlands, one of the District's poorest neighborhoods, so that I could examine, on assignment for The Washington Post, the problem of teen-age pregnancy. I had planned to stay four to six months; I stayed a year.

It was a hot day in late July when I moved into the apartment, one of 14 units in a three-story brick building on the corner of Fourth Street and Valley Avenue SE. No one appeared to take much notice. Within a few days, however, I learned from a neighbor that I had attracted attention, that people were wondering who I really was.

They knew, even from a distance, that I was different. Although I am black, although the neighborhood is overwhelmingly black, it was immediately clear from my clothes and my speech that I was "not from Southeast," as one neighbor put it.

My old jeans, my brightly colored African shirt marked me as someone from another place. The way I talk reflected my life and my work: I am 41, a native of Harlem in New York City, where I grew up in a middle-class enclave called Riverton. In 1965 I came to Washington to attend Howard University, and I have lived here ever since.

I was no stranger to poor communities. In my 17 years as a Washington Post reporter, my assignments have taken me to the District's poorest neighborhoods, and I have written extensively about how heroin had destroyed the lives of many young people. I also spent nearly five years as a Post correspondent in Africa, where I had visited and lived in areas overwhelmed by poverty, famine and disease, more devastating than anything I had seen in the United States. A World Unto Itself

But none of this quite prepared me for living in Washington Highlands. After several months there, visiting its churches, walking its streets, meeting its people, I realized why. Washington Highlands is a world unto itself, cut off from even the rest of Anacostia by the crescent-shaped Oxon Run Park. It is a neighborhood of hard-working people, struggling to protect themselves against the drug dealing and street crime that plague the community. They have a way of sizing up strangers, of determining their motives and their intentions.

Shortly after I moved in, I called a community resident, Gloria Bookard, on the recommendation of a friend. I told Bookard, a social worker at nearby St. Elizabeths Hospital, about my project. She immediately became angry. "Why did you choose out here?" she said. "I get angry about outsiders who come in here and try to speak for the community."

There is an answer to Gloria Bookard's question.

I went to Washington Highlands because it is one of the poorest communities in the city, with one of every three people living below the poverty level and with more families receiving welfare payments than in almost any other area of the city, according to census data. At the same time, it has more teen-age parents than almost any neighborhood. In 1984, one of every four babies in Washington Highlands was born to someone between the ages of 13 and 19.

Here, I thought, was the place to examine teen-age pregnancy, to get beyond the government studies and commission reports warning that babies born to teen-agers are at a greater risk -- more likely to die in infancy, more likely to grow up in poverty, more likely to drop out of school and, therefore, less likely to get jobs.

Before I moved to Washington Highlands, several well-meaning friends, black and white, told me what I would learn about teen-age pregnancy. Some said poor, black girls have babies because their lives are dreary and they see the baby as something to love. Others said the girls had babies to get more welfare money. No one talked about the motivations of the fathers.

Neither prediction turned out to be true. Certainly, welfare and a need for love are important forces in Washington Highlands, but they often have little or nothing to do with why some boys and girls start having sex as early as 11 years old, sometimes intentionally to get pregnant, often reject birth control or use it recklessly. When I told this to friends and colleagues, some refused to believe it. I stopped telling these people about my experiences in Washington Highlands.

This series of articles centers on the lives of teen-age mothers and fathers, the attitudes they reveal and the motivations they hide, the fantasies they hold and the realities they live with. Partly because of the choices they have made and partly because of the conditions they must endure, they are truly at risk -- and because they are at risk, so are their families, their futures and the communities around them. A Question of Trust

On warm summer evenings, residents of my apartment building at 3900 Fourth St. SE would gather on the front steps, hoping for relief from the humidity. About two weeks after I moved in, I joined a group on the steps and struck up a conversation with Charles A. (Willie) Hood, 21, someone who had lived all his life in Southeast Washington.

Nearly everyone I met in the first few months treated me with suspicion and hostility. Willie was no different. A few days earlier, he had confronted me and demanded to know my real reasons for moving into Washington Highlands. He intimated that I was an undercover narcotics officer who was pretending to be a newspaper reporter so I could infiltrate the extensive drug network that operated in the community.

He told me, "People keep asking, 'Who are you?' You're not from Southeast. You don't look like you into the life here."

He finally accepted that I was a reporter, but he was still suspicious of my motives. So when I saw him again on the front steps that night, I invited him back to my apartment. There, he tried to advise me about how to approach people.

"Keep a low profile," he said. "A lot of people are curious about you. Be nonchalant as possible. This is not your neighborhood. I trust you, but if anything happens, I don't want to be the blame for it."

Then, he warned me that I was playing a dangerous game. "You don't know how evil this part of Washington is, do you? . . . You a college graduate, right? You see, you're a gentleman. I still don't know exactly what you're looking for in Southeast . . . . Your curiosity brought you here. But you know curiosity killed the cat."

He was not through. "By being a reporter, trouble will come to you . . . . People are hiding so much. Your six-foot height and nosy reporter questions put fear into people. People ask themselves, 'What do you want to know about me for?' "

He was right. It took months to meet people and earn their trust, and then months more before people revealed motivations that seemed to be genuine. The conventions of journalism -- asking questions and hoping for a straightforward answer within just a few minutes -- were a barrier to getting at the truth. Only by interviewing some people as many as 12 times, usually in sessions that lasted several hours with a tape recorder running, did I learn some of the most important details that appear in this series.

I learned early on that dates and appointments were of little importance. Several times, I found myself losing my temper after being stood up for interviews. One man stood me up five times in two weeks. I finally caught up with him only by scheduling an appointment for early in the day, when I hoped he might still be in bed. He was in his underwear when I interviewed him.

After five or six interviews, many of those interviewed grew comfortable enough to divulge bits of family gossip, tell a ribald family story, curse without embarrassment and chide me about being single. For some, I became a confidant where none had existed before.

Some people never did feel entirely comfortable talking with me. One teen-age mother, Boochie Williams, acknowledged after our first interview that she had not been candid. "You come across just like a counselor," she told me. "Asking so many questions." So, she said, she gave me the kind of answers she would give a school counselor -- fudging things here, hiding things there.

The interview clearly made her nervous. "I'm not used to people asking me these questions," she said, as I asked her to describe how she got pregnant at 16.

She told me that the pregnancy "was just something that happened." She knew little about birth control, she said, blaming herself for not paying more attention during a sex education class she took at Hart Junior High School. When I pressed her about this, she became even more uncommunicative. The interview ended after only 45 minutes.

Several months later, Boochie's older sister, Theresa, told me that Boochie had taken birth control pills for a long time, but had stopped at some point. Finally, 11 months after our initial interview, Boochie told me just how long -- she said she starting taking the pills when she was 14, two years before she got pregnant.

Over the course of the year, several people told me one thing in early interviews. Then, over time, slowly at first, the layers began to fall away -- and they told me something different. One girl's mother, Melba Smith, gave the simplest explanation for the reluctance of people to answer my questions.

"What you are doing is an intrusion," she said. A Neighborhood Walk

In 1984's waning summer days, Willie Hood and I went on extensive walks through Washington Highlands, a square mile of streets filled primarily with government-owned and government-subsidized apartments. We walked past some buildings that were deceptively new looking, the result of renovation work that included new windows and doors. But others were marked by the familiar symbols of decay and vacancy -- boarded-up windows and broken screen doors, abandoned tires and crumbling concrete parking lots.

We passed few shops on our walks, only an occasional drugstore or corner grocery. The neighborhood's anchors are not commercial stores but institutions: several public schools, a health clinic, a score of churches and day care centers. In that respect, Washington Highlands mirrors the rest of Anacostia, which is home to several large government installations but has no manufacturing plants of any size, no good-sized supermarkets, no movie theaters, no subway line, and fewer doctors, cars and jobs than any other section of Washington.

During our walks, Willie told me about himself: that he married at 19, that a child was born soon after and that another was due in a few weeks. He also told me about his troubles finding a job, about dropping out of high school, about how he nearly became a father when he was 16.

He was in the ninth grade at the time, a student at nearby Hart Junior High School, older than many of his classmates. He vividly recalled how he felt when his 15-year-old girlfriend, an eighth grader, told him that she was pregnant.

"I almost dropped to my knees," Willie told me. "I grabbed her and hugged her. I was happy!"

But his reaction startled his girlfriend, he said. She wanted an abortion. Now, Willie said, it was his turn to be angry. "I will really expletive you up," Willie said he told her. "Don't you ever let anything happen to that baby." She pretended to agree, Willie said, but she went ahead with the abortion.

After a brief breakup because of the abortion, Willie began to see her again. By this time, however, the girl was using birth control pills, or "birth controls," their nickname in Anacostia. That changed their relationship, Willie said.

Because the girl would almost certainly not get pregnant, Willie said, "I couldn't really feel like a man."

Willie, like many of the teen-agers interviewed for this series, did not worry much about the future, about how his life might have changed if he had fathered a child at 16. Living for the moment is part of the teen-age culture in Washington Highlands, a culture that suggests that sexual activity at a young age is a normal part of growing up.

Veda Usilton, a junior high school counselor for girls at Friendship Educational Center in Washington Highlands, said she has come to accept that most ninth graders, and many younger girls, are sexually active. "It's stupid to teach abstinence, so I preach birth control," Usilton said. Fending for Themselves

A few weeks after I moved to Washington Highlands, I went jogging one rainy August morning. I left my apartment on my usual course, which took me along Valley Avenue, up 13th Street and up Southern Avenue before it turned down Wheeler Road. As I reached the 3800 block of Wheeler Road, I saw a young-looking mother holding an infant in her arms and trying to keep track of two boys walking behind her.

The younger boy, who looked about 3, clutched an umbrella but seemed to be having trouble with it. He was dragging its curved handle along the ground, and that seemed to irritate the woman.

"Carry that umbrella right or I'll slap the expletive out of you," she screamed at him. "Carry it right, I said . . . . " and then she slapped him in the face, knocking him off balance.

This incident was extreme, but I often saw teen-aged parents cursing and cuffing, and I occasionally saw them striking their children. Early in their lives, these children learn that violence is one way to relate to people. The violence is not only against children; men hit women, women hit men, spouses hit each other. Often, the violence is triggered by a perceived affront to someone's dignity.

Children also learn to fend for themselves, such as the 6-year-old girl in Charmaine Ford's apartment building, who was left by her mother to care for herself and her 7-month-old sister. One day, I talked with Willie Hood's father, Charles E. Hood, who runs a termite control business in Anacostia and is a pastor at a fundamentalist Christian church in Northwest Washington, about children caring for themselves.

Hood told me about a family where, he said, an 8-year-old girl was the most responsible member. He described the family: The girl's parents were both alcoholics, frequently unable to accomplish even basic household chores. As a result, the girl in effect took care of her two younger brothers, who were 4 and 5, Hood said.

One October night, Hood and I climbed into his tan-colored, secondhand Mercedes-Benz and went to visit them. When we arrived, the 8-year-old girl was playing outside. When she saw Hood, she stopped and went inside with us.

We sat down in the kitchen, where the two young boys immediately huddled around me, apparently eager for attention. I tickled them and they climbed onto my lap, giggling and laughing. Their mother suddenly noticed the ruckus and grabbed the 5-year-old. The boy bowed his head. The mother then slammed him on the back with the palm of her hand, yelling at both of them for bothering me.

The girl sat on a chair in the corner, silently watching the entire scene.

NEXT: One mother's struggle to survive