Nervous chatter faded into silence with the countdown, as a group of metropolitan area high school students watched the monitor in WETA's (Channel 26) Arlington studio, knowing their turn on the air would follow.

Ten sonar-like blips later, the faces of their comrades appeared under the lights as Joseph Benti opened the program "Why in the World" by introducing Harry Rositzke, author and retired CIA officer, and five students from Arlington and Montgomery counties and the District.

Benti and Rositzke were powdered; the students on the set were not. Their faces glistened slightly with perspiration and their hands fumbled nervously as Rositzke boomed on about Soviet-American relations. Occasionally one of them would venture a meek interruption. There were gasps among the group watching the monitor one flight above. Was this what was in store for them? It wasn't what Roger Kennedy, director of Smithsonian's National Museum of American History, had in mind for the group he was about to take on the program.

"We aren't going to do any of that," he said, drawing eyes away from the monitor. "Right? None of this, 'Tell me, Mr. Great Man.' "

A free soda for every time they interrupted with their own ideas, promised Brad Stein, a teacher from Lemuel A. Penn Career Development Center.

A dime for every time they don't say "hopefully," Kennedy said. The students' faces broke into smiles.

Half an hour later, the producers were beaming as the second group of students kicked around their ideas and Kennedy's in an informal, searching discussion of how the past reflects upon the present. That, the producers said, is what the program is all about.

"It's deceptively simple," said Benti, a former news anchorman who, besides moderating the "Why in the World" discussions, produces the program at KCET-TV in Los Angeles. "We take 28 minutes to examine one question."

Benti and executive producer Barbara Barnes-Vyden have spent the last year working with a $1 million grant from General Motors Corp., taking the show to studios throughout the United States and Canada. They sit down with high school students and discussion "guides" who have included attorney F. Lee Bailey, authors Ray Bradbury and David Halberstam, academicians, federal court judges, scientists, newspaper editors, poets and corporation executives. Among the questions aired over 191 public television stations: "Why in the world . . . does Shakespeare help reveal how terrorists think? . . . do some people avoid legal responsibility? . . . should we care what happens in Poland? . . . is there surplus food? . . . are some newspapers like dinosaurs?"

Benti envisions someday expanding the program so that students in California could converse with experts in New York. The idea for the series, now at the end of its first year, came from Walter Cronkite, who, according to Benti, wanted to get beyond the "razzle-dazzle, blue smoke and mirrors" of network news and help to make students aware of how world events relate to studies.

"An absence of relevancy makes students think education doesn't have any value," Benti said. Producer Barnes-Vyden said the series has been a hit in educational circles, and stations have asked to carry the program next year, but future funds are uncertain.

Mary Gregal, a senior at Washington-Lee High School, said being able to converse with experts gives students a chance to understand how issues affect their lives.

"It's good for everyone to be able to ask questions, and not just watch an interview," she said. And the interplay of world events, she said, "gives me an idea of what the future's going to look like."

Gregal was accompanied by Cynthia Day, a student at Yorktown High School, who appeared on the segment discussing U.S.-Soviet relations.