Six videotapes stacked neatly in the office of Loudoun County School Superintendent David N. Thomas told the story of his small role in the continuing thaw between the Soviet Union and the United States.

With titles such as "A Day in the Life of the Soviet Union," the tapes served as Thomas's primer for a trip this week to schools in Moscow and Leningrad, a visit that Thomas considers a sort of cultural diplomacy between the countries.

"It is the exchange of people, and people getting to know each other, that will strengthen the relationship," Thomas said. "I think it's a really exciting time to be visiting . . . . There will be a lot more open dialogue."

With eight other educators, including several from Washington and its suburbs, Thomas left for the Soviet Union on Monday from Dulles International Airport.

Thomas said he plans to return on Tuesday.

Arnold Rosenberg, a Rockville school principal, and Mark Mullin, the headmaster of St. Albans School for Boys in the District, also were scheduled to go with the group.

Although exchanges of Soviet and American students have been under way for several years, this trip is the first of a group of superintendents and principals. Because of the tumult in the Eastern Bloc, it almost didn't happen.

William Parrish, of the National Association of Secondary School Principals, said the trip fell together a few months ago. The association organized the venture, Parrish said, to highlight the importance of educators having a world view.

"The U.S. is a part of a world community," Parrish said. "We hope to gain insight into how Russians operate."

Thomas, who is paying $1,000 for the trip out of his own pocket, said he watched the videotapes and read a recent book about the Soviet Union to prepare for his brief visit. Although known for its rigid schools, the Soviet system could provide some intriguing lessons, he said.

"I'm sure the Russian educational process is in a state of flux," said Thomas, who planned to take along school yearbooks, literary magazines and gym shirts as gifts. "It might, on reflection, change our perspective."

Soviet pre-kindergarten programs, for example, begin earlier and are more ambitious than those in Loudoun County, or in most places in the United States, he said. He wonders whether that might give students, rich and poor, a better chance of academic success.

Another difference involves the number of years every student must attend school. In the United States, most students attend school through age 18, but in the Soviet Union only the best students continue in school beyond the age of 16, he said. That makes their high schools more elite, he said, but Thomas questions what such a system would mean for late-bloomers or less-ambitious students in this country.

Thomas said he was especially interested in the rigorous way Soviet schools teach state-approved political philosophy, religion, economics and other subjects. He wants to see whether Soviet students and educators agree with the approach.

"I would be interested to see how kids respond," he said.