A few months ago, Todd Jones was working in his grandfathers tobacco fields in Stony Creek, Va., a few miles south of Petersburg. The money, he said, was "good" -- he could take in $30 for a day's work, and as much as $40 if he went from 6 a.m. to 6 p.m.

Jones wanted something more out of life, but saw few other opportunities for a 10th-grade dropout.

Then he heard about the Job Corps. Against his mother's wishes, Jones joined and was sent to the Potomac Job Corps Center in Washington.

Life was difficult at first, recalled Jones, whose Job Corps roommates "laughed when I said 'down yonder' instead of 'over there,' " and jokingly called him a " 'Bama," (for Alabama).

But Jones has been at Potomac for three months now, learning to be a brick mason, and he is beginning to like it: "Everything they got is here to help you. The teachers, they're here to help you."

Ray Spell, 18, of Richmond, came to the center at about the same time as Jones. Spell joined the Job Corps, he said, because "I wasn't doing nothing else."

Like Jones, Spell is a high-school dropout. The Job Corps, he said, is not like high school: "In public school, they be telling you what to do. The instructors here be cool. They show you what to do, give you an example. After that, you're on your own."

There are about 500 other young men and women at Potomac. Almost all are black. Most are from Washington and Virginia. Two-thirds are male.

They stay at the center for an average of six to nine months, training for jobs as airline reservation and railroad clerks, bricklayers and hospital aides. They live in government-owned buildings, behind a chain-link fence, and are watched day and night. They are awakened for work at 6 a.m., ordered to remove their hats while eating and allowed to leave the center only briefly.

But they live in air-conditioned rooms with desks and sometimes a framed print on the wall, they are shown movies every night, they have a swimming pool for their sole use, they go on trips to Washington's Kennedy Center for the Performing Arts and to King's Dominion amusement park. And they are paid to study: $40-$100 a month, plus a graduation bonus.

After graduation, the majority of students, with the help of the Job Corps, will get jobs. During fiscal 1980, Potomac's post-graduation employment rate was more than 70 percent.

The Potomac center is one of more than 100 Job Corps camps in the United States. Southern Virginia has three: Old Dominion near Lynchburg, and Blue Ridge and Flatwoods, both near the Tennessee border. But Northern Virginia has none, so the Potomac center, along with the Harpers Ferry, W. Va., center, takes in a lot of Virginians.

Set up as part of Lyndon Johnson's "Great Society," the Job Corps at the end of the 1960s was what one observer called "probably the most unpopular antipoverty program with Congress."

Earlier this year, however, Sen. Orrin G. Hatch (R-Utah), a prominent conservative, called the Job Corps "a government training program that provides jobs and saves more dollars than it expends."

President Reagan's budget cutters apparently agreed with Hatch: The Job Corps program is slated to receive an increase of $67 million in fiscal 1982 over the $560 million it was given in fiscal 1981.

The Services Division of RCA Corp. gets about $5 million of that each year to run the Potomac Job Corps Center under contract with the Department of Labor. RCA takes youths from poor families and tries to turn their lives around. The cost per person per year is $9,440.

Potomac Center Director Nellie Williams, who has spent more than a decade as a Job Corps teacher and administrator, said the key to success is that the Job Corps is a residential program, permitting corps members to become immersed in the habits of the workaday world.

Just how that immersion takes place can be seen on a short walk through the center.

Rosella Scott, a native of Lynchburg who teaches bricklaying and cement masonry, acts like a foreman and dresses his "crew" in the overalls of union bricklayers. Scott has placed 16 Job Corps graduates in the cement masons' union in the last two years.

The same philosophy is at work across the street, where teachers from the Brotherhood of Railway & Airline Clerks (BRAC) train their students to take airline reservations and shunt railroad cars.

At the building's entrance, BRAC's Norman Cyr has placed two time clocks and a rack for time cards. Arriving late earns the card-holder a red circle. Just to the left of the clocks hang two copies of railroad rules and regulations.

"To get them into good habits," explained Cyr, who spent 27 years with the Boston & Maine Railroad before becoming a Job Corps teacher.

Facing the time clocks from the other side of the hall is a display case containing photographs of graduates now working as railroad clerks. One of the most recent is Petey Mills of Forest Heights, Md. On Aug. 10, Mills was hired by the Baltimore & Ohio Railroad at a salary of $15,000 a year.

Other corps members learn to be hospital and child care aides, air conditioner repairmen and business clerks. They all follow the "flip-flop" system, alternating weeks of occupational training with weeks in the classroom devoted to reading, writing and arithmetic. Courses are given on personal hygiene, personal finance, family planning and cooking on a budget.

James White, 19, of Richmond, said he feels the Job Corps is misunderstood by the public. "Many people feel the Job Corps is for dropouts, for people on the streets. It's wrong. The Job Corps is a training program for American citizens," he said. White, currently president of the Potomac center's student government, plans to begin college next year.

At the end of each day, corps members return to their dormitories, which are cleaner and better looking than many college dormitories. That was not always so, said David Shinton, the center's business manager.

Proud of what he calls his "humanization" program, Shinton shows his visitor the new color-coordinated lounges, the new shower tiles installed by corps members and the new soft lighting on the ceilings.

Nellie Williams has a succinct reason for giving corps members comfortable quarters: "You don't take people out of dumps and put them into dumps."

The Job Corps is open to men and women 16 to 21 years old who are out of school and unskilled. They must be from a "disadvantaged" background; for a family of four, an annual income of less than $8,450 is considered disadvantaged. There is no educational requirement.

There are more applications than places, meaning an average waiting period of four to six months between application and enrollment.

Corps members who get involved in fights or refuse to obey orders are placed on work details and denied weekend passes. (About 75 percent of the center's corps members go home each weekend.) Repeat offenders are invited to resign; if they refuse, they are expelled. Last year, 68 corps members were expelled.

Sitting on the fence after dinner, six corps members seem happy with the rules.

Asked what they think of the Job Corps program overall, they respond together: "Good."

What would they be doing if they had not joined Job Corps? The answers come slowly, quietly, one by one.

"I'd be locked up."

"I'd be in jail too."

"I don't know. Looking for a job."

"Hustling. Jail."