On the day the yellow buses started to shuffle suburban white children with city black children last September, Mary Jean Baratta chained herself to a telephone pole in front of her neighborhood school and sent her three children to a hastily located private school.

Despite the fact that the Los Angeles Unified School District had, after months of debate, adopted a court-ordered desegregation plan, "I never believed they would actually do it," said Mrs. Baratta, widow of a rent-a-car entrepreneur.

Her protest rated front-page notice, but the buses kept criss-crossing the vast expanse of the city, keeping children on the road for up to four hours a day.

Now, as the school year nears its close, Mrs. Baratta's children are back in public schools. But the city's desegregation program is in trouble. Because 31 per cent of the white children have fled, many schools in the bus routes are still segregated. They have only been moved to new neighborhoods.

For this reason and many others, the district plans to cut back on busing next year. And the voters, largely because of continued opposition from white parents, will face a constitutional amendment that would limit state courts' power to order desegregation.

Amid all the fury, however, little note has been taken of how the program works for children who ride the buses daily. So one recent morning I joined the passengers on one of the longest elementary school routes, from the neighborhood of the predominantly black 42nd Street School to Oso Elementary, in suburban Woodland Hills.

With Mrs. Jessie Guest at the wheel, the bus made its first pickups in a block where stucco houses in make-believe Mediterranean styles stand behind small, well-tended lawns, then moved on to shabbier blocks near the bleak main thoroughfares.

The children talked softly or gazed out windows as the bus wheeled onto the freeway, across the still-wild Santa Monica Mountains and into the San Fernando Valley, a vast expanse of houses and the stronghold of Bustop and other groups committed to ending "forced busing."

"If you ask me about school, I'd rather not go," said 12-year-old Tawnya Easley, a 6th grader. "I can learn everything I need to know from my mother and my brothers and sisters. But they give us nice homework, especially on Tuesdays and Fridays when we don't have any." Besides, she said, her mother expected her to grow up and be able to do something better than the domestic work she has been forced to take on.

Twenty-seven miles from the start of the route and more than an hour later, the bus pulled off the freeway, wound along a few curving streets, past homes nestled in greenery, and stopped before the single-story, pink-and-grey Oso School.

Tawnya took two pink curlers out of her hair, stuffed them into the pockets of her tan-hooded jacket and hurried with the other Black children toward wooden tables set under an overhang in the school yard, there to breakfast on Rice Krispies, milk and a hot dog under the wary eyes of a monitor. The white children, who were not taking part in the breakfast, gathered at the far side of the yard. There were not many. Oso Elementary, in a neighborhood that is almost exclusively white, is nonetheless 81 per cent black - a de facto ghetto school imported from the city.

"You the reporter? Interview me," a girl at one of the tables shouted. The children had been told I was coming. "Write down that I don't like coming here so early in the morning. I like the school just a little bit on Fridays when it's PE. I wish I were at 42nd Street School because there was good food and a nice principal. But I'm glad they put us with white kids."

Others crowded around. "I liked the way the teachers were better at 42nd Street," said a small girl. "But here they teach you more," put in a 6th grader named Paul.

When it was class time, the monitor, a woman with a tense angry face, hurried the youngsters away from the tables. Her voice was metallic when I asked how things were going. "Fine, just fine," she replied, with the sound of a steel door closing.

An hour into the day, disorder held sway in the classroom where some of the older children (14 black, 2 Asian, 4 white) were grouped for reading. The teacher was explaining owrd usage. But throughout the room there were furtive exchanges, secret tussles. The underlayer of anger in the teacher's voice acknowledged he was not in charge.

A girl named Dena rose from her seat by the door and lazed across the room to reach for something under a front desk.She seemed to ignore the teacher when he told her to return to her seat, but she did slowly start moving back. Then suddenly she and another black child where slugging at each other. The teacher lurched forward to break it up. He led her back to the solitary seat by the door, scribbled something on a piece of paper, handled it to her and sent her out. He returned to word usage.

"You should be here when the violence is at its worst," the slim blonde classroom aide whispered to me.

"When is that?" I asked.

"Oh, recess, lunch. They fight all the time. Constantly. With each other, mostly. Not fit for being with civilized people, some of them," she said. "I wouldn't want to be a teacher. Like my husband says, I'm here to protect the teachers from the others. But I'd be the first out the door, I'll tell you."

Later, over coffee in the sunny yard, the teacher said that in 23 years he had never had a fight in his classrooms before this year. He had taught in predominantly middleclass white schools. But now he faced "disrespect for authority" and disruption.

"To get a hold of parents is difficult," he said. "Some don't have phones. Often they work and you have to try at night. But that's a long distance call [to the city] and I won't call on my own phone."

The same morning, in another classroom, a quite different scene transpired. I stopped in several times and always found children intent over books and papers. Mrs. Naomi Finkel spoke softly. There was no need to shout. She moved from desk to desk, working with children individually. Later, I asked her how she managed so well.

"My expectations are high and they meet them," she said. "I never lowered my expectations."

"These children from 42nd Street are just adorable," said Joyce Clarke Parkinson, the principal. "They're what?" I asked. She looked at me across her desk, from under long mascara-laden lashes. "Adorable," she said firmly.

"It's just a handful of behavior problems. This problem of respect for authority . . . Mexican-Americans are trained to respect anyone bigger or older. But with black children you have to prove your authority before they'll accept it," she said.

"Almost all the problems are within the same racial group," she continued. "We do have one standard: against fighting. Every parent and child received a copy of the standard. But you're contending with long-established habit."

Was there a counselor for students and teachers? Only three days a month, she said. She herself does what she can, but she knows that as the principal, a person of administrative authority, she can not do the job needed.

Betty Matthews, a cheerful woman who has the title of integration coordinator at Oso and is also the math and reading resource teacher, was in her classroom with four Asian children who had recently moved into the neighborhood. They had arrived at Oso in September speaking no English.

New bright faces were glued to flash cards she held up for them, and they giggled and tongue-tripped in eagerness to pronounce the words and tell their meaning. Mrs. Mathews' face was as bright and eager as the four small ones.

"Their parents don't speak English either," she said after the class ended. "But they're just dying for them to learn. They're so motivated." She sighed. "This is my 33rd year. I've had some really sharp classes - 140, 150 IQ's. I've got a whole file there for all kinds of things for sharp students to read. It's no use to me. Now it's a lot of remedial reading we need. It's a whole new ballgame."

The student body at Oso is not only different this year, it is different every semester. The "flip-flop" scheme designed to make busing more palatable to white parents has children from Oso and nearby Calvert schools assigned to the predominantly black 42nd Street School in the city half the year and to their home school the other half.

However, Oso also has some black children from another black school, 97th Street, who come under a voluntary program. These stay all year. So do some white children who, for various reasons, are exempt from the arrangement.

The district is spending $120 million this year on the desegregation program, mostly for transportation. Buses are provided not only during regular hours but also later, in case some children want to stay at the school yard till five. "This is to further integration, with the idea that they'll get to know our neighborhood," said Mrs. Matthews. Can they roam in the neighborhood? No, she said. They stay in the school yard.

"They tend to be a lot more physical," she said when asked if fighting was a problem. "We've been told in their culture this is a way they often settle their differences. We were told this by black leaders. Where with our kids, they'd go to the teacher."

Dena sat in the outer office, droopily copying lists of words from a book. What was that fight about, I asked when were were alone. She said the child she had hit had whispered "your mama . . . " to her, and those were fighting words. The teacher was unfair, she complained. "He'll punish just the kid who hit back but not the one who started it."

Dena had come to Oso not because, like most of the black children, whe was assigned, but because she and her mother thought there were more educational opportunities here, she said. Like homework. In her old school, "the kids play hooky a lot," she said, "and my momma doesn't want me to drop out of school. I don't either."

But now she guessed she'd be sent back to 97th Street, and she said she was glad: "I don't like the way they treat us here." Besides, at 97th Street she had seconds on food free, while here, even if you got free breakfast and lunch, you had to pay a dime for extra milk and 50 cents for a whole second tray. Sometimes she didn't have the money.

Also, added Dena, she didn't like all the fighting here at Oso.

"Look, look how they gang up on each other," a blond girl was saying, pointing at some black children who were running across the school yard. "See? They're after someone. And they say they're gonna get us. On the day of the school picnic there's gonna be a big fight."

A clutch of white girls stood together, watching events across the yard. "A lot of people say, 'If there's busing next year, we're moving,'" a smaller girl told me. "I went to 42nd Street last semester and I didn't learn as much. They were doing multiplication where we were on decimals already."

"One white girl was already raped by three black boys. They locked her in the bathroom," another girl said. (Responded Mrs. Parkinson: "I listened to both sides of the story and I feel both are exaggerating.")

Further inside the yard, Inbal Brozki, 10, munched a sandwich. She had been bused last semester, she said, and wanted to be bused again, even though she hated catching the bus at 6:45 a.m. and "when you get off you can't move your legs."

How was Oso different this year from last, I asked her. "Last year there were hardly any black kids here. Now they've taken over our school. There is fighting." And at 42nd Street, is there a lot of fighting? No, she said.

The 42nd Street School is an older two-story building in a quiet, comfortable black neighborhood. Despite the student exchange with Oso and Calvert, only 6.8 per cent of the children here are bused-in whites.

The day after visiting Oso, I dropped in unannounced and visited all classrooms involved in the desegregation program. In each children worked quietly. No disruption was visible. During recess, there was no visible hostility in the yard. I spoke to teachers, aides and children.All said there was no big problem with fights.

"I anticipated it, but it's no worse than anywhere in the Valley," said a teacher who had chosen a two-year stint at this school after years in an affluent Jewish suburb. "But I'm told this is one of the more desirable inner city schools."

Mrs. Juanita Johnigan, who is black and one of the older teachers here, remarked: "If you make children understand that you are their teacher and their friend you won't have fights. I don't allow it to start - and then I want to know what is the problem. Maybe I can help."

Mrs. Johnigan, who plays the koto and speaks Japanese, Mandarin Chinese and Tagalog, has been at this school for more than 10 years, arriving originally as a substitute when the students were largely Asian.

"These children had had a white teacher, and they didn't want me," she recalled. "So they did everything they could think of to harm me." After a paper clip flew at her and almost hit her eye, she said, "I stood up and said, 'Look, I'm here and I will be here.' Then I went to every child's house - there were 36 children - and I visited the parents. After that I had no more problems."

At 2:45 p.m., Oso's black children board their bus agin, restless and noisy. As they pile in, a small blond boy scoots past on his skateboard. A woman walks by with a white poodle. The hour back will be longer.

Just before the bus wheels onto the freeway, several children crane toward a window and point: "Look, horses!" Then it's across the mountains again and back to Crenshaw Boulevard with its billboards, its clutter of gas stations, fast food corners, used car lots and cheap supply stores.

Among the children who walked home from Oso was Michelle Baratta, daughter of the woman who had chained herself to a telephone pole. Michelle's younger sister would be taking the yellow bus back from 42nd Street School, but she was exempt from being bused because a doctor had certified that she had a tendency to get car sick.

"It was to keep them off the bus, not to keep them from being with Mexicans and colored people, that I put them in private schools last fall," said her mother. But the private school had turned out to be too expensive and not so good, she said, so she had accepted the inevitable for this year, while working for the initiative that would restrict court power to order busing.

The ballot measure, proposed in the legislature unsuccessfully in previous years, passed this year after a court-appointed experts proposed that desegregation be extended to 100 school districts in the region to avoid white flight.

That measure might not affect the Los Angeles program. But the school district is already moving to curtail it. For of the 129 elementary and junior high schools involved in the mandatory busing arrangement, 37 have failed to show 30 per cent white enrollment, the required minimum.

So the children at Oso are due to be reshuffled again next year. Many will again go to what are officially called "racially isolated" schools. Even if the desegregation program had worked, more than half the district's 550,000 children were to have remained in such schools. The program that is about to be dismantled was a limitedand costly experiment. CAPTION: Picture 1, no caption, UPI;Picture 2, no caption, AP