Although most of the city's summer youth employes had retired by 6 p.m. last Thursday, many were still busy rehearsing plays, music and dances to be presented in the District through Aug. 14.

More than 11 performing arts organizations participating in Arts D.C. Summer Youth Employment Program have been preparing to offer entertainment to the community.

The series of public performances began last month with a performance by the African Heritage Dancers and Drummers' summer workshop at its Northeast studio.

The program continues at noon today, when the Everyman Street Theatre Company of dancers and singers performs Motown hits at Gallery Place in Northwest, and 6 p.m. at Mayfair Mansions in Northeast.

At noon tomorrow, the performers will be at Grant Park Care Center in Northeast, then at Meridian Hill Park in Northwest at 6 p.m.Also tomorrow, D.C. Contemporary Arts will premiere its musical "What He Could've Been."

The performance will run nightly through Aug. 16 at Fletcher Johnson School in Southeast.

The play, written by Adrian Bolton, who studied and performed in New York, tells of a young singer whose promising music career is stunted by drug use. Capitol Hill Arts Workshops' Air Conditioned Players will present a satirical revue titled "Sketches O'Comedic Entertainment" at the Capitol Hill Arts Workshop theater in Southeast tonight and tomorrow night..

For information on times of performances, call 547-6839. Cosan Summer Arts Institute will present dance, music and poetry at the Western Plaza in Northwest at noon today.

At 1 p.m. Tuesday, the young performers will appear with the Ellington Jazz Ensemble at the Ellington School. Also Tuesday, World Music Youth Ensemble, a summer workshop at the Levine School of Music, will perform original compositions that blend upbeat African swing with classical European music under the direction of Robert Northern.

The 14-member ensemble worked five weeks arranging and rehearsing scores for the performances.

During rehearsals, the members interchanged roles as composers and directors, and each played two or three instruments.

Their next performance will be at 6 p.m. Tuesday at the Pavilion at the Old Post Office. The Blues Alley Cats, students working at the Georgetown nightclub, a summer youth workshop, also will perform at the Pavilion Tuesday night. The D.C. Youth Ensemble performs at noon Tuesday at the Pavilion and 6 p.m. at Ellington. Wednesday, the group will put on another show at noon at the Western Plaza.

The finale will be at the Market V Gallery at the Eastern Market on Capitol Hill. The Summer Youth Program of Market V Gallery will present "Rehearsal for a Murder" at 8:30 p.m. today through Sunday.

There also will be an art exhibit in the halls surrounding the stage. Expansions Art Collective will present portions of its original revue at 6 p.m. Monday at the Pavilion. From Aug. 13 to 15, the group will stage its full-length production, "Halfway Down From Cloud Nine," at 8 p.m. at Takoma Theatre and at 6 p.m. Sunday. As part of its "Jazz For The Sometimes Forgotten" series, the Lettumplay Summer Youth Jazz Ensemble will offer concerts at noon tomorrow at Children's Hospital, 2:30 p.m. Saturday at St. Augustine Church's "Family Day," and Aug. 13 at the Rose Garden of the Walter Reed Army Medical Center in Northwest.

All performances are free and open to the public.

Another project of the summer youth jobs program is is a mural painted by young artists at 14th and W streets on the Martha's Table soup kitchen building.