Her mom and dad were thousands of miles away on a historic European diplomatic mission, but Susan Ford was making some modest history on her own back home. She played host to the first high school senior prom ever held in the White House. Susan, 17, who is headed for Mount Vernon Junior College in the fall, invited 73 graduating classmates of the exclusive Holton Arms School in Bethesda, Md.—and their dates—to 1600 Pennsylvania Ave. In the East Room, they did "The Bump" to the music of two rock 'n' roll bands, the Outer Space and the Sandcastle. In the State Dining Room they drank spikeless punch and munched on Swedish meatballs, quiche and chicken in sweet and sour sauce. "I'm having a great time," the jersey-gowned Susan coolly observed, "but it's really like any other prom we've had."

Many of her friends were less blasé. It isn't every teenage prom goer whose date had to be cleared before the dance by the Secret Service and whose chaperones included White House aides and microphone-jabbing newswomen.

The Class of '75, which paid $1,300 for the prom out of class funds, petitioned headmaster James Lewis to ask Susan if she could arrange for them to use the White House. One classmate put it in simple teenage English: "No one in the class didn't want it here."

Susan's date was 21-year-old William Wainright (Billy) Pifer, a premed student at Washington and Lee University and the son of a doctor. Susan and Billy met on a blind date at the Shenandoah Apple Blossom Festival in Virginia, where Susan was crowned festival queen last month. "We really hit it off," said Billy. "My parents haven't met him yet," Susan admitted, "but they will, for sure. I'll invite him again." (Susan dropped her long-time beau, Gardner Britt, of Arlington, Va., after a quarrel over her support for the Equal Rights Amendment.)

One reason the dance may have seemed anticlimactic to Susan was the lavish pre-prom dinner she and Billy shared aboard the presidential yacht, Sequoia, with three other couples. As the yacht steamed down the Potomac, Susan and her guests ate beef Stroganoff on rice and sipped wine. (The White House said Susan would foot the bill for the dinner out of her own pocket. The Navy, which operates Sequoia, would not disclose the tab.)

Being nothing if not a traditional girl, Susan and Billy were driven in a White House car to a friend's suburban home for a wee hours party of champagne, cake, music and a pre-dawn dip in the pool. Was Susan given any instructions by her parents before they left? "They told me," she said, "to be good."