"CUZZINS" -- At The Rep Inc., 3710 Georgia Avenue NW. 291-3904. Saturday and Sunday at 3, through September 6. Adults $6, under 12 $4.

Four five-year-olds in tutus and tap shoes bring down the house with disciplined funk in "Cuzzins," The Rep Inc.'s third production from the children's summer theater workshops. They bounce onstage to a heavy disco beat, mimicking the teenage "Super Sole Sisters," who bump and grind in the same production number. The wee ones kick, smile and shimmy, each coming close enough to the group routine to suggest lots of practice.

Kids in the audience were as charmed as their parents. Ingrid Murphy, a ten-year-old from Reston, said the littlest girl dancers were her favorites. "It made me want to take dance lessons," she said. Andre Hagood, 13, from Northest, watched his cousin Arletta Batts play Sarah Big Mouth. His favorite part was when she came to borrow a bucket of sugar from her neighbor. "I like the story more than the dancing," he decided.

The Rep workshops, from which the cast is assembled without auditions, have yielded a tight product. For an amateur production housed above a commercial stretch of Georgia Avenue, the show is imaginatively choreographed on a slick set. The cast of some kids, ages four to 15, carry off the razzmatazz with humor and poise.

"Cuzzins" updates Aesop's tale of town-versus-country mice, drawing urban/rural contrasts with time out for tap, African, disco and modern dance steps. The big-city cousin sniffs at ham hocks, collard greens, blackeyed peas and sweet potatoe pie offered by the "hick" cousin at her laundry-draped trailer. She meets neighbor Sarah Big Mouth, true to form, and watches her corn-fed kids dance for the "movie-star kin." Country cousin is then whisked off to endure fast-paced city sights -- a purse-snatcher, burglar, jive-talkin' flower-seller and, of course, Disco Dan ("I'll show you how to put a dip in your hip"). After a night of boogeying and a dream sequence reprise of the characters, there are lessons learned.

When the monologues pack heavy meanings, the kids sound stilted. "I've read of the inspired visions of the '60s, lived through the narcissism of the '70s, and can't deal with the apathy of the '80s," discourses Darryl Williams, 14, as Disco Dan. But the simpler messages come through: "Even though we're different, we're still very much alike," grass-roots Juanita (Tonya Duncan, 12), concludes about her urbane relative.

(After the show, Tonya, an eighth-grader at Suitland Junior High, explained why she thought she was cast as Juanita: "Now and then I just talk country," she said. "And I've always wanted to be an actress.")

Other than forced words like "narcissism," the acting is natural. Partly because some of the dialogue sprang from workshop improvisations, according to playwright Art Jones, a Fairfax County schoolteacher. There are enough soliloquies to go around, and at last weekend's opening performance nobody blew a line. Usually in the nick of time the script's weak moments are saved by Sadiqa Pettaway and Aisha Kahlil's engaging choreography.

Certain cast members switch roles on alternate days during the show's three-weekend run, but Sole Sister Rhonda Crutchfield continues as a dancing standout, equally at home with disco struts and African folk movements. She's 15, a Positive Pisces, planning to dance on Broadway and become a doctor, the playbill notes.

Other critics on the aisle approved of the performance. Eric Brown, a four-year-old from Southeast whose cousin Randy Nelson plays the long-legged flower man, liked the dancing best. He was proud to note Randy was also the stage manager. And Alice Murphy, 11, singled out the opening farmhouse scene as her favorite part.