Big Al Carter, with biceps the size of a grown man's thigh, doesn't favor subtleties.

"Listen, listen, listen! Please!" he yelled at about 35 high school kids, who, dressed in paint-blotted T-shirts and jeans, were adding a spectrum of colors to a smooth wall 20 feet high and about as wide. "This paint has to be put on the board. I don't want any paint over there."

The youths, part of an Arts DC mural painting project at 71 O St. NW, did not snap to attention as they continued filling in the spaces on the nearly complete mural. This bothered Big Al.

"Hey!" the compact, heavy-set boss growled. "Listen! I want everybody working. I don't want anybody playing games."

For Big Al, a professional artist and substitute high school art teacher from Arlington County, summer does not mean a vacation in the sun, unless one considers it soothing to supervise 35 novice artists and coordinate the design of the chromatically complex mural.

Facing a shelter for the hungry and homeless, the mural is a psychedelic depiction of three crowned men eating. A teary-eyed bird in the corner of the painting represents the hungry. At the beginning of the project, when Big Al asked for design suggestions, one student suggested painting a group of people eating out of trash cans. Big Al quickly rejected that suggestion, and sketched instead an upbeat, almost biblical design for his charges to color.

"See that 'D'? That 'D' is very shaky," Big Al told a painter. "It needs to be gone over very carefully, like the 'W.' "

By noon, Big Al was sweating, in addition to having a lovely pink color on his skin. This was unusual, since Big Al is black. The paint from the mural glowed in his hair and on his beard as well, but he didn't notice. He was too busy checking brush strokes, making sure the ladders were safe and keeping everyone active.

"Hey man, look!" he yelled at one painter who moved in the wrong direction. "They got to finish it over there!"

Big Al couldn't believe the students were reacting so slowly. "What did you all eat for breakfast, anyway?"

"A lot of them say I'm like a sergeant in the army because I'm so hard, but I'm only doing that so they can learn things right," said Big Al, who has been heading mural projects for about four years.

Most of the students said they didn't mind Big Al's constant chants of "Get to work," "Tighten it up" and "Be consistent," and said his perfectionism has made them better artists -- and workers.

"He taught me how to keep a steady hand, paint better, be more creative with my work," said Tracy Young, 17, of Franklin Roosevelt High School.

"Sometimes I find myself working to do a good job, not just for myself, but to impress Al," said Wayne Charles, 16, of Benjamin Banneker High School.

"Al's like a big brother to me," said Eddie Lea, 17, of Calvin Coolidge High School.

Mural painting, part of Mayor Marion Barry's summer youth employment program, allows the 35 youths to learn a craft and earn minimum wage for 30 hours each week.

They began July 2 on their first series of projects, for the SOME (So Others May Eat) building, where a private organization provides free food and medical care to the indigent. A shiny "Plaquebusters" mural looms inside on the wall of the waiting room for the clinic's dentist. In a room where the homeless can bathe, painted aqua drops of water cascade down the wall, bearing the message "Shower." The most ambitious design, however, is the huge mural facing the building.

Before they began the project, the youths ate a meal at SOME and watched the hundreds of people standing in line for free helpings. "I knew there was a lot of bums and stuff on the street, but I didn't realize so many people would line up for food," said Natalyn Norman, 15, of Regina High School.

By 11:15 a.m., more than 60 men waited patiently for their meal as they watched the youths paint. Some looked at the mural, but most stared straight ahead without talking.

The students said they'd received plenty of favorable comments. "They come over all the time and tell us they like what we're doing," said Wayne Charles.

Students got involved in the project either for a love of art, money or a little of both. For Lawrence Duncan, 16, of Duke Ellington School of the Arts, mural painting will give him some of the skills he will need as an artist, and perhaps help him earn an art scholarship to college.

Duncan said one of the highlights of the program was the group's three-day visit to the Department of Labor, where students learned how to present portfolios and what career options exist in the art world.

Natalyn Norman explained her pragmatic reasons for getting involved in art: "If I can't become a doctor like I want to, maybe I can become a fashion consultant or draw designs for clothes. It's something I can fall back on."

Wayne Charles minced no words: "I'm doing it for the money, and it's something I like to do."

Lunch hour crept closer, and soon the line for the food grew longer and the students began drifting from their ladders and resting their paint brushes. They talked in groups, as Big Al quieted down and let his workers take a break.

They have six more murals to finish in the next few weeks. Big Al, who has displayed his own art at the Corcoran Art Gallery's Washington show and the Anton Gallery, will be a busy man until Aug. 16, when the program ends.

"It'll drain you," he said, "but I perk back up at night with my kids and sit down and draw."