YOUNG VISIONS OF A COMMUNITY -- Opens Thursday. Through Aug. 21. Selected photographs and writings from 100 D.C. public school students who participated in the Literacy Through Photography project. S. Dillon Ripley Center, 1100 Jefferson Dr. SW. Free. 202-628-7856.

ALEXANDER AND THE TERRIBLE, HORRIBLE, NO GOOD, VERY BAD DAY -- Opens Friday. Through July 17. A play based on Judith Viorst's book about a day full of cavities, lima beans and ugly sneakers. Glen Echo Park, Adventure Theatre, 7300 MacArthur Blvd., Glen Echo. $7. 301-320-5331.

START WITH THE ARTS -- Friday, 9:30 a.m.-4:30 p.m.; Saturday, 10 a.m.-5 p.m. A festival featuring art activities and story hours, plus dance, puppet shows and theater performances by Joint Forces Dance Company, Kids on the Block, Imagination Stage and more. Union Station, 50 Massachusetts Ave. NE. Free. 202-628-2800.

DINOSAUR BABIES -- Friday at 10, 11:30 a.m. and 1 p.m. A prehistoric story and puppet show. S. Dillon Ripley Center, Discovery Theater, 1100 Jefferson Dr. SW. $5, children $4. 202-357-3030.

8TH ANNUAL SOUTHERN MARYLAND SOAP BOX DERBY -- Saturday, 9 a.m.-3 p.m. Watch kids compete for a chance to race in the All-American Soap Box Derby finals in Akron, Ohio. Derby Hill, Washington and Fenwick streets, Leonardtown. Free. 301-863-2561 or 301-475-9791.

REACH FOR THE SKY -- Saturday, 10 a.m.-3 p.m. A family day featuring more than 24 aircraft including a U.S. Marine Corps Harrier, Fairfax County Police helicopter and a U.S. Air Force Predator unmanned aerial vehicle. Plus discussions with pilots, hands-on activities and stories. National Air and Space Museum, Udvar-Hazy Center, 14390 Air and Space Museum Pkwy., Chantilly. Free. 202-633-1000.