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 Montgomery and Arlington counties and the District of Columbia.

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 a student ventured 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 the Smithsonian Institution's National Museum of American History, had in mind for the students 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 the District's Lemuel Penn Career 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 tells about 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 on the air with experts in New York, as reporters and newsmakers now talk on television news shows. 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 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.

Bruce Plotkin, a Winston Churchill High School junior, said he likes the idea of the show.

"I never really put together the perspective from others' surroundings before, to be able to look back in history," he said. "It's better to be able to look at the whole picture to see what's really affecting us."

Plotkin was accompanied by Daniel Mendelson, a Walt Whitman student who appeared on the segment discussing Soviet-American relations.