After four hours of cruising in a car - and at least that many beers - a group of Jeb Stuart High School students stopped at a red light.

One boy in the group was challenged to do something "fun" in the car stopped alongside. He accepted. He jumped out and threw a billiard ball through the other car's windshield.

The youth was found guilty in Fairfax County Juvenile Court of malicious vandalism and could have been jailed. Instead, before sentencing, he was referred to a probation counselor who as also a social studies teacher at Jeb Stuart.

The student admitted to the counselor that what he had done was "really stuipd." [WORD ILLEGIBLE] revealed that the student's parents had just separated. On the basis of the counselor's report, a judge placed the student on probation. He has not been in trouble again.

Such happy endings are the result more than 75 percent of the time at the 15 Fairfax County high schools and intermediate schools that have probation counselors.

The program, now in its fifth year, pays teachers an extra $1,800 a year to serve as counselors. They are formally deputized by the county juvenile court, and half their salaries are supplied by the court, half by the school.

Ultimately, the counselor's job is to submit a written report to a judge about a student's prospects for probation. The report is based on interviews the counselor conducts with the student, his parents, his teachers and occasionally his principal.

But along the way, the counselor - who tends to be young and male and without formal counseling or psychology training - tries to help the student examine why he has committed a crime and what his underlying problems are.

Counselors make it a point not to talk to other students about a student who is in trouble, for fear of undermining him in the eyes of his peers. Nor do counselors accept incriminating information about anyone without first warning a student that anything he says will be relayed to a judge in the counselor's pre-sentence report.

"The whole program turns on the question of trust," said Steve Peck, 29, probation counselor at Jeb Stuart for the past three years. "Some of them think I'm a 'narc,' but after a while most of them realize I can be trusted . . . Most of the kids I have tell me the truth."

"There's often a great deal of defensiveness and apprehensiveness at first," said Bud Mayo, 33, who was named a probation counselor at Lake Braddock High School this year.

"But a lot of times, showing a kid you care is what makes a success story. I can't tell you how many times I've heard: 'Hey, I acted like a jerk.'"

A dozen students interviewed in the halls at Lake Braddock agreed that the counseling program is an inventive and effective way to help students in trouble.

"From what I hear," said one senior, "most of the counselors are young, which has to be a big plus." Another senior said she was aware of the program, but unaware of the names of any fellow students involved in it. "That has to make you trust them," she said.

Eric Assur, probation supervisor of the central unit of the Fairfax County Courts, said the program has worked "very, very well" from the court's viewpoint.

His only regret, Assur said, is that relatively few county schools participate. Only 15 of the county's 44 intermediate and high schools have a counselor.Two schools have two counselors each.

Assur said money is available if more schools want counselors. But he said many principles either do not see the need for one, or prefer to channel students in trouble to the guidance staff. "The principal pretty much has the final say," Assur said.

The Fairfax County probation program is the largest in the Washington area. Arlington County has an older, but smaller, program. No exact equivalent to probation counselors exists in Alexandria, Washington or the Maryland suburbs.

Peck and Mayo said the range of students referred to them is far wider than "classic" juvenile delinquents.

Mayo, for instance, said he works with students who are leaders at their schools, and with "the kid who has broken into houses for the hell of it." Peck said one student he counseled was "the model of everything you could ask - 'Yes, sir' and 'No, sir' all over the place. The other kids would be shocked to learn that he wrote $1,000 in bad checks.

Cynicism is a problem with some offenders, the counselors said. "You're not going to get locked up the first time, and they know it," Peck said. "Sometimes you just can't break through the bitterness," said Mayo.

"How much have I helped? I don't really know," said Peck. "But if you figure that the idea is to break down that wall that gets built between kids and adults, well, I pride myself in being able to do that."