The blonde 13-year-old girl in faded jeans and tight tan T-shirt came before the juvenile judge, clasping a pack of Marlboros in her hand. Her head cocked slightly to th left, her eyes locked on the ceiling, she slumped into a chair on the left side of the room - the side for the accused.

The girl's mother, who entered the room behind her, nervously straightened her print dress, smooth her back hair, then sat down on the side of the room - where the prosecutor would sit if this were a real trial.

But the woman was not a prosecutor [WORD ILLEGIBLE] 13-year-old was not a defendant, the proceeding [WORD ILLEGIBLE] that was about to begin before Montgomery Juvenile [WORD ILLEGIBLE] John C. Tracey.

[WORD ILLEGIBLE] mother had driven to the Court [WORD ILLEGIBLE] afternoon from the family's Potomac neighborhood of expensive, split-level homes and spacious backyards to her evidence that her daughter was "beyond parental control" - a "child in need of supervision" in the language of the juvenile code.

Her daughter had run away to Indianapolis, stolen the family car and wrecked it, and taken drugs from the medicine cabinet. Last summer, said the mother, by now crying, "my daughter began her sexual activities.

It was a mother's admission that she could no longer cope with her teen-age daughter - or no longer wanted to try. She was turning to the court to take the child off her hands by placing the daughter in a foster home or some other institution where she would be supervised by counselors.

The woman and her daughter are part of a trend, experts say. There was a time when misbehaving teen-agers were quietly disciplined in the home and such problems were kept within the family. Parents seem now to be turning more and more to the courts and outside agencies for help.

The Potomac case was one of about 6,000 handled over the past year by the Maryland Department of Juvenile Services. In Maryland, the children are [WORD ILLEGIBLE] need of supervision, [WORDS ILLEGIBLE] they may be called [WORD ILLEGIBLE] children," unruly children or [WORDS ILLEGIBLE] of the court."

They are not considered juvenile deliquency because they have not necessarily committed any crime. They have been brought to court not by a police officer but by parents [LINE ILLEGIBLE] pushed to the breaking point of despair by children whose offenses may include skipping school, drug use, running away, fighting, promiscuity or worse [WORD ILLEGIBLE]

A white mother from Kentland in Prince George's County, for example, brought her 4-year-old daughter to court in part to separate from a boyfriend who was black. A woman from Clinton charged her son with being "beyond parental control" after his girl friend became pregnant.

The families are just as likely to come from affluent suburbs as from urban slums, according to statistics. Many of them come from single-parent homes, like the Potomac girl who appeared before Judge Tracey a few months ago.

There was a period, her mother told the judge, when her daughter kept running away. "Sometimes it was overnight. Sometimes it was as long as eight days when I didn't know where my daughter was.

"She took my car twice . . . The last time was when she had a cast on her leg. That time she struck a road sign. But even then she didn't stop. She continued on and sidewiped another car."

The young girl fingered her pack of ciagarettes and looked up occasionally at her mother as she spoke. He tight-fitting clothes revealed the figure of a 20-year-old woman, but her face was round and soft - not quite child, not quite adult.

"There were promises, but they were always broken," the mother continued. "Just before she ran away the last time, we were dancing together in the kitchen, you know, kidding around because she had the cast on her leg.

"My goal is to have my daughter with me. But I'm frightened about the summer.What's going to happen while I'm at work?"

She finished by asking the judge to place her daughter in a group home for juveniles where she would receive 24-hour supevision and psychological help form trained youth counselors.

"Do you have anything to say?" Judge Tracey asked the girl. "I want to be at home, but when I get into trouble, I don't want to be on restriction, so I run away. I don't give myself time to think about what I do, I just do it," the girl replied.

She told Tracey she wanted to go to a group home "to get my head straightened out."

"What type of things disturb you about your home?" the judge asked.

"Well, my father. He doesn't let me come visit him. he doesn't take part in family counseling. He doesn't hardly care."

The girl's parents were divorced two years ago. Her mother's boyfriend now lives with the family.

"Do you take drugs?" the judge asked.

"I smoke pot, sometimes hash. I've used Thai stick (a strong strain of marijuana from Thailand)."

"Why do you choose this outlet?"

"I like to get high."

"When do you think you'll be able to return home?" said the judge.

"When I work my problems out."

Judge Tracey sent the girl to a "shelter care" home, where a group of teen-agers with similar problems lives with counselors. After two months there, she was returned to her Potomac home because of a lace of space in county foster-care facilities.

Both she and her mother had wanted her to stay in a group home.

"Even though I'm sending you back home," the judge finally told the girl, "today you will start a new life."

"Yeah," the girl replied.