Clarence is 12 years old, black, shy, withdrawn, out of phase with society and possibly a genius. He is a fictional character, but not very fictional.

A son of migrant laborers from the South who have recently moved to New York, Clarence has never learned to read, although his aptitude test results are the best in his school. He spends most of his time in the hallway outside his classroom, because the other kids laugh at him when he tries to read, and that leads to fights.

Clarence is the invention -- or maybe the discovery -- of Robert Gardner, an independant black filmmaker, whose first feature-length film, "Clarence and Angel," had its Washingtn premiere this week at the AFI Theater. Gardner is also the writer, producer, director, fund-raiser, publicist and sole proprietor of the film, which won prizes at the Locarno Festival in Switzerland and has been shown all over Europe.

The idea for "Clarence and Angel" was born in a college hallway, while Gardner was resting between examinations."I saw a guy who was laughing to himself," he recalls, "and I asked him why. Here he was taking college examinations, and he told me, 'I never learned to read until I was 13.' He was a son of migrant workers, he got into trouble because he couldn't read and he spent a lot of time out in the hall.Then he met a Puerto Rican kid who taught him to read. That was the basic story. Angel teaches Clarence how to read.I never saw that guy again; he has no idea that his story has been made into a movie."

"Then I started asking my friends, 'What was grade school like for you?' And my friends trusted me with little pieces of information which I gradually fit together. I wanted to get a perspective on childhood; the whole picture is shot from a child's height, so that whenever the camera looks at an adult, it is looking up. And I wanted to include the parts of school experience that we forgot. We tend to remember only what was nice and edit out all the rest."

The picture cost $85,000 to produce and took four years to make: "Three years to raise the money," Gardner explains, "three-months to rehearse it, 3 1/2 weeks for the shooting and the rest for editing."

After writing the script and raising the money (partly from foundations and other non-profit sources, partly borrowed from friends), Gardner began casting, using only two professionals in a large cast. "I looked for faces I liked," says Gardner. "One role was taken by a man I met on a bus." One of his central characters, as assistant principal, works in a New York liquor store. The principal sells tokens in the subway. Gardner spent months going to neighborhood theaters and sitting in classrooms, picking out children for his cast. Darren Brown, who plays Clarence, was found in a New York school hallway after he had been ejected from a class for disciplinary reasons.

Although the odds are stacked heavily against Clarence, the picture has a happy ending -- after Clarence's extroverted friend, Angel, finally realizes that Clarence's problem is illiteracy and Clarence turns his stubborness to the job of learning rather than rebelling. Perhaps the most striking part of the picture is its success in showing elementary school life from the inside. Variety called it "an unassuming film that uses sentiment without mawkishness and delves into a world of pre-teen-agers and school life without condescension or false moves."

"Clarence and Angel" was chosen to inaugurate the 1981 Black Film Institute, sponsored by the University of the District of Columbia, which will show one film each week until the end of July. After that, it will be taken on a 10-city tour as part of a traveling film exhibit, "Black on Black." It has not yet been shown in commercial American theaters, although it has been booked for runs in Atlanta and New York.

"Local boy makes good, huh?" says Gardner, who was born in the District of Columbia in 1948. He went to school here, graduated from Eastern High School, and left town 15 years ago "because Washington at the time didn't have anything I could use." He traveled around the country, worked at unskilled jobs in California, Chicago, Detroit and St. Louis, and finally saved saved enough money to study journalism and filmmaking at McGill, Columbia and CCNY.

"One advantage of being an independant filmmaker with a low budget is that you can take all the time you need," says Gardner. "But it would be nice not to have to count pennies, and maybe to be paid for my work." He is now discussing the possibility of directing a film based on the book, "Train Whistle Guitar," which may have a budget of as much as $750,000 -- small by Hollywood standards but enormous to Gardner.