My son made his off-Broadway debut recently. The sixth-grade musical at Wyngate Elementary School in Bethesda is probably as far off Broadway as you can get--but even Laurence Olivier had to start somewhere.

Two months ago, Jeremy, who normally considers the shower too public a place to sing, casually announced that he was trying out for the class musical. The name of the show must remain nameless since, in the furor of creativity, nobody remembered to ask the authors for permission to produce their play.

Actually, the script was rewritten considerably, making it short enough to keep the kindergarten audience from becoming restless, yet expansive enough to provide parts for all 90 sixth graders. It is doubtful that the authors would seek credit for this particular production.

Suffice it to say that the plot concerns an orphaned girl and a wealthy man with paternal instincts. Our son secured the role of the multimillionaire.

Two months is hardly enough time to prepare for such a theatrical tour-de-force. I rushed out and bought the Broadway album and soon our housekeeper was claiming she heard the songs in her sleep. The plumber fixing our frozen pipes was singing duets with our daughter Meredith. Only the star refused to cooperate. He kept sneaking off to listen to Buckner and Garcia sing their new hit, "Pac-Man Fever."

Rehearsals were postponed during Christmas vacation and suddenly it was five weeks before opening night. The "orphan" was growing rapidly, as sixth-grade girls are wont to do. If she didn't slow down, she soon would be taller than her stage father. We practiced good posture and prayed.

With four weeks to go, we concentrated on costume design. Grandfather's derby was sent special delivery. The music teacher, obviously unaware that the hat was an authentic period piece, vetoed the derby because it fell over Jeremy's eyes. The star agreed to wear the first pair of real shoes and non-sweat socks his feet had seen in at least three years. I conferred with other mothers about costuming the hobos and the tattered orphans in a style befitting a Bethesda production. The hobos, it was decided, would wear casual caps from Britches and the orphans' tatters would be color-coordinated using frayed designer labels.

With three weeks to go, panic was mounting. I asked the orphan's mother to stop feeding her vitamins until the show was over.

With two weeks to go, the plumber had mastered the hand gestures and was practicing a dance number with grandma, who had flown in from New York to attend the premiere.

With one week to go, word was out that the dress rehearsal was a disaster--a featured player's voice changed right in the middle of his big number.

On opening night, a star was born in Bethesda. Socko! Boffo! The Variety lexicon is too limited to capture the excitement in the school's all-purpose room. One critic, crying and clapping at the same time, was heard to exclaim, "It was worth every Pamper I ever changed."

Of course, the male lead's part was cut down a bit to make room for the other 89 players in the 30-minute production. But what poise! What projection! I swear, the kid grew three inches while on stage.

Before the spotlight fades, I am plotting his next career move. He thinks he is going back to gym hockey. But I hear that the Harlequin Dinner Theater is casting "Bye Bye Birdie" and then there's the Burn Brae. . . . I wonder why nobody at Wyngate Elementary thought to invite Father Hartke to opening night.