For most of the ride, the busload of Prince George's senior high school students sat quietly, waiting to be dropped near home. Suddenly, without warning, according to the bus driver, "all hell broke loose."

"kids were jumping over seats, shouting, hitting and screaming, 'i'm going to whip your ass,'" recalled driver Doris Lehanan. "one boy yelled at me to get my fat ass back there and break it up. I just pulled over to the side and told them to get out and get out quick."

That unruly episode was not unusual, according to many county school bus drivers and students. Each day as nearly 80,000 students in Prince George's and millions more nationwide commute to school by bus, similar incidents occur. "We have a PR problem with the taxpayers. It's hell out there and no one knows anything about it," said Harold Shaw, an official in the union that represents the county's 800 school bus drivers.

Like some of the public schools the students attend, pupils on school buses often are undisciplined and disruptive, simmering on the edge of violent outbursts. For six out of 10 students in Prince George's the ride is a daily ritual.

"It's okay, It's no big deal," said one 10th grader recently as he slouched in his bus seat with a halfsmoked cigarette behind his ear. "You just sit there. Usually nothing too interesting happens."

From the driver's seat, however, the point of view is quite different. "You're just one person with 40 kids and you never know what's going to trigger them off, or when you're going to get your brains knocked out," Lehanan, a five-year veteran driver, said before setting off on her rounds. Even school officials, who normally are reticent when discussing school system problems, admit that trouble occasionally breaks out on bus rides. "Things are not as calm as they used to be," one school official said. "those drivers are the unsung heroes of the school system," added Allan I. Chotiner, the deputy superintendent.

Last year, for instance, a woman bus driver was attacked as she drove some high school students home. Earlier this year, with school in session just a few weeks, another bus driver was attacked twice by her charges.

Drivers say that fights break out even among elementary school children, some of whom, they say, direct rapid-fire expletives at each other and the drivers.

On one recent bus ride, some young girls who attend William Beames Elementary School in Suitland arrived at their nearby apartment complex only to begin arguing and pushing each other. One little girl, no older than 8, refused to get off the bus without the driver's protection because a much larger sicth-grader had threatened, as the smaller one put it, "to kick my butt."

Gloria Savage, the driver of that particular run, said that fights used to break out every afternoon and only recently calmed down under the watchful eyes of parents who now meet the bus.

Savage said that elementary school runs, while increasingly troublesome, are easy for drivers to handle because the students are young. It is the junior high school students that concern the drivers most, she said.

Pointing to a line of buses outside Andrew Jackson Junior High School in Suitland recently, Savage offered a visual explanation. The students are hanging out windows, jumping up and down on seats, pushing each other and ignoring all commands or requests by the drivers.

On one bus, an eighth grade student, who is sitting near the front, leans out a window and, spotting a smaller boy in back, frowns, makes a threatening face and gestures at the boy with his middle finger. The smaller boy, on crutches, retreats. Several girls, wearing dresses or tight-fitting jeans, some with belts slung around their hips twice, walk past the bus carrying books, 45 rpm records, and hairbrushes. They ignore the eighth grade boy, even when he taunts them with, "Hips, move those hips. Boy that [girl] got some hips."

The girls settle onto another bus and gossip about other students, compare successful shopping sprees and complain about school. "They switched me to a new science class," one girl with a Farah Fawcett style haircut whines," and the teacher smells bad and spits when he talks to you. I ain't staying there."

One group of junior high students from the Camp Springs area is notorious among the bus drivers. "i won't take that run any more," said Barbara bruck, who has been driving for five years. "They ripped up the seats. There was rubber everywhere. They tore up the whole bus, with anything they could find."

Savage said she had that run once, too. "They smoke pot, cut up the seats, write on the ceilings and we have to clean it off," she said.

On that run several years ago, Savage's bus broke down, forcing her to leave it and call for help. In the 15 minutes that Savage was absent a girl on the bus allegedly was burned with cigarettes and matches by other students, according to the girl's mother, who filed a suit against the school system. The suit was later dropped.

Although fighting among students occurs, bus drivers said that it rarely overlaps into confrontations with them. "Sometimes they threaten you but you don't say nothing when it happens. You just remember and don't pick that run the next time," said Buck.

Although some drivers said they believe that discipline problems have become severe only since busing for desegregation was ordered in Prince George's in 1973, most drivers and school officials report that racial incidents are not common. Instead, they say that the lack of discipline on the buses is a mirror image of what goes on in many classrooms.

"what makes the biggest difference to us is how the principals and the school administration handle the kids," Savage said. "With a supportive prinicipal, we generally have a lot fewer problems."

Marie Sommers, a bus driver with the school system for 11 years, said she has another solution. "What kills me is the way parents bitch and complain about us drivers. If they rode on these buses one day, they'd never say a word again . . . and they'd never let their kids act the way they do."