AT AN AGE when most would-be directors are doing super-8 film exercises at film school or working as gofers, John Gray, 23, is directingan episode of the $3.5 million "Powerhouse" series for the Educational Film Center of Annandale, Va., because he figured that if you want to make movies, you should just go ahead and make them.

The scene is F Street in Foggy Bottom and Gray is lining up a shot of the "Powerhouse" kids as they walk down the steps of their clubhouse and get into their van. They are carrying maps and an overstuffed picnic basket. The script has the actors teasing 13-year-old Jessica Prentice about how much food she has packed and she makes a wisecrack. Jessica is not biting into her line right. It is not a crucial moment in the script but it adds to the texture. Gray takes her aside. "I want you to come back faster on that line," he encourages gently in his older-brother voice. "Be a little more smart---."

The cast walks through the shot again and Gray doesn't like the deserted street. Seeing two white-haired ladies watching the scene from a stoop across the street, he beckons with his finger. "Ladies," he announces in his grandson voice. "I'm going to make you a star." One of the women isn't buying it. "Am I gonna get paid for this?" Gray gives them a cue to walk through the shot with their backs to the camera. "Action."

Flashback:

When Gray was 17 he found an ad for AFI grants in a film magazine. "I did the application and sent them a 10-minute black-and-white job I had done in high school." He got the grant and the result was "The Weekend," which won awards at film festivals in Malta and Rochester, N.Y.

His next film was "The Patriot Game," about the troubles in Northern Ireland. The film cost "five grand" to make. The money came from a bank which loaned him $1,500 for a vacation. When that was gone he "got hold of some credit cards" and went to the limit on two or three of them (he's still paying them off). He used a considerable amount of Irish charm and got a lot of people to work for free and shot the film on the docks and cobbled streets of his native working-class Brooklyn. He edited the film at night at August Films, a New York production house where he started his career editing Hanna-Barbera cartoons. It was shown on cable TV in New York.

Eventually it came to the attention of Linda Marmelstein at Daniel Wilson Productions in New York. When they met she was a little taken aback by the fact that Gray was only 21, and though she thought him talented, she didn't know what kind of work there could be for a 21-year-old director.

But having got his foot in the door, Gray started a vigorous campaign of self-promotion.

First, he sent a letter to the production house with one sentence written all over it: "Let John Gray direct." A week later he sent a singing telegram with the same message. The third week balloons arrived at the producer's office: "They're real cheap, 50 cost $10." The message on the balloons? You guessed it. "Let John Gray direct." Finally, a huge chocolate cake was sent. The inscription on the icing: "Let etc."

Marmelstein was asked by E.F.C. if she knew any young talent and recommended Gray. He flew down to Washington for an interview, but E.F.C. was leery about letting someone so young direct.E.F.C.'s offices were soon being filled with balloons. Gray thinks the coup de gra ce was "a photograph of me on the Bowery begging with a tin cup." So in November 1980 the company let him direct a 15-minute short about a 12-year-old with a drinking problem, called "The Glug." Gray admits, "It's not 'Gone With the Wind.' " But it showed he could handle himself. Ira Klugerman, the "Powerhouse" series producer, decided to let him direct an episode.

"Powerhouse" is a cross between the Bowery Boys and "The Electric Company." A group of youngsters who belong to the fictional Powerhouse club have 16 episodes of adventure, each one teaching them a lesson about growing up. Negotiations are in progress now to have the series air on PBS in the fall of 1982.

Flash-forward:

By the third take, Jessica still hasn't found what Gray has in mind. He takes her aside. On the next take she fizzles entirely, hardly getting the line out. The ladies, meanwhile, have improvised a bit of their own and stop and turn to look at the kids getting in the car.

Gray smiles, "Ladies, if you don't mind, please keep going until you hear me say 'cut.' We won't pay you more if we see your face." The crew lines up the shot one more time. "Action." Almost everything works: Jessica's line reading is as sassy as Gray wants. Ah, but the ladies -- they forget their cue: "Ladies, you blew it. You could have made your screen debut. That was the one."

Gray is under contract with E.F.C. until May. And after that? Why not apply for one of the prestigious AFI fellowships that would allow him to work on the set of a major feature? "Well, I would have to move to L.A. and I don't have a car so I'd have to buy one. They really don't pay much. I figure it would cost me $15,000 to do it." He pauses. "For $15,000 I could make a movie."