The Sterling High School concert band, complete with electric bass and vibes, was at one end of the Kennedy Center's South Gallery yesterday, blaring out Stevie Wonder's "I Wish;" at the other end, Celeste Holm couldn't keep still. Making her way through the other people attending the day-long conference of the National Committee on Arts for the Handicapped - Sterling is a school in Brooklyn, N.Y., for the emotionally and mentally retarded - her left leg kept moving to the beat.

Holm, a board member of the National Association for Mental Health, earlier had told the conference. "Ever since I was 3 and saw Pavlova on stage in New York I've wondered why some people appreciated art more than others, why they were more human.

"Shaw said, 'Next to torture, art is the most persuasive thing in the world.' I say, 'If it doesn't art.'

Holm at 59 is trim, her once-blond hair silver. Under her arm was one of the pen-and-ink drawings by 26-year-old Quentin Nalla that she and other speakers at the conference - including conductor Sarah Caldwell and painter Jamie Wyeth - had received. Nalla is a local handicapped artist.

"In July I'm going out to Hollywood to do a movie," Holm said. "'Backstairs at the White House,'" and she grinned.

"I'm going to play Mrs. Warren Gamaliel Harding. That poor girl was a little handicapped herself, having Mr. Harding for a husband."

She won an Academy Ward in 1947 for her performance in "Gentleman's Agreement," but Holm has not done a film in a few years. She has been busy with her work for the mental health council and the Creative Arts Rehabilitation Board in New York.

"We have a 65 percent recovery ratio (at the rehabilitation board). Some of these people have been under custodial care in homes for years. Using the arts for aiding human development - it's the new page being turned," she said. In the meantime, her show-business career has been on the back burner.

"Yes," she replied hesitantly, "but the kids are what I'm interested in now."

At lunch, Caldwell and Wyeth debated the merits of various Cambridge, Mass., book stores.

Sen. Edward M. Kennedy (D-Mass.), who had come to address the conference through the offices of its chairman, his sister Jean Kennedy Smith, was chafing at the delay as technicians wired the podium for sound.

Sen. Kennedy delivered a 10-minute speech to warm applause, and was halfway out the door when he was called back to pick up his award, a painting by a handicapped artist. But even Kennedy was almost ignored compared to the people swirling around Holm. "Of course, darling," she said in reply to a question one matron, "After all, for the kids, now is the only time we'll ever have."

"The role I've always wanted to play is Mrs. Roosevelt's understudy, Holm said. She wanted everybody do as much as they could do. She uncovered a yawn. The day had begun early, and she still had to visit the National Institute of Mental Health before flying back to New York.

The lunch ended with the singing sign language - the whole conference had been translated simulataneously for the deaf. Holm, who 35 years old began her career by bringing down the house singing "Cain't Say No". In "Oklahoma," sat at table, waving her arms and moving her fingers in a sign language rendition of "Rock My Soul in the Bosom of Abraham."