Guida Ferreira, chief of the Barbadian mission to the United Nations, was keeping one eye on the United States delegation during the committee debate on refugee relief assistance and disarmament.

"Basically," she said, "We vote like the United States."

The Barbadians, four on that committee, were sharing the round table with two delegates from El Salvador, in a rare yet calculated display of Third World solidarity among the frequently feuding nations of Latin America and the Caribbean.

Regional and ideological blocs and alliances, solidly united on some issues but with that unity precariously fragile on others, are as much a part of the United Nations as the formal committee structures. That Barbados and El Salvador could come together on the issue of superpower intevention in the region is just one example of the kind of lesson that doesn't come from textbooks on foreign affairs.

The Barbadian delegation consisted of 14 students from Bethesda-Chevy Chase High School. As participants in a model United Nations sponsored by Georgetown University, they learned about the world and the changing nature of international relations.

Last weekend, about 2,400 students representing 165 high schools from across the country turned the ballrooms of the Shoreham Hotel into U.N. conference halls and caucus rooms for Georgetown's 18th North American Invitational Model United Nations.

The schools are assigned the roles of specific countries, far enough in advance to give them time to research the history and current foreign policies of their country. The BCC students, for example, began preparing in early November for the role of Barbados.

The Maryland area schools represented included BCC, Landon High School and Holton Arms in Bethesda, Connelly School of the Holy Child and Bullis High School in Potomac and Bowie Senior High School.

In their roles, the Maryland schools were often at the center on the revolving stage of world events.

Bullis, for instance, played the politically delicate role of Vietnam, a nation that came under sharp attack in the model forum from nonaligned nations concerned about the Vietnamese invasion and occupation of Cambodia. (The Cambodian government deposed by the Vietnamese was played by St. John's College High School of Washington, adding a little inter-jurisdictional rivalry to an already tense international situation.)

Meanwhile, Landon students came under similar fire on the nonintervention question in the role of Afghanistan. That delegation had to fend off charges from Third World countries and the Western bloc that its government was a Soviet "puppet" that did not represent the Afghan people.