Thang Nguyen, a 20-year-old tenth-grader at Montgomery Blair High School in Silver Spring, has the appearance of the average American high school student: Collar-length hair, blue jeans, a red sweatshirt, running shoes and books tucked under his arm.

Raymond Bien-Aime, a French-speaking tenth-grader who left his native Haiti by boat in 1980, sports well-tailored designer jeans and has a liking for pizza, spaghetti and McDonald's french fries.

Carlos Oviedo, an 18-year-old political refugee from El Salvador, is a basketball fan who, like many of his American classmates, likes to dance to Kool and the Gang and The Police.

Beyond these surface predilections, Thang and Raymond and Carlos and the other 500 foreign students at Blair have little in common with most of their American peers. For the foreigners, high school hardly resembles the yearbook memories etched in the minds of most Americans.

Whether they came to the U.S. from Vietnam, Haiti, El Salvador, Cambodia, Cuba, Jamaica, Nicaragua, Lebanon, India, Pakistan or any of dozens of other countries, these students view high school here as a refuge.

Like the Eastern Europeans who migrated to America at the beginning of this century, the new foreigners see school as the first step to learning English, obtaining a green card and getting a job that will produce money for family members back home. It is part of life in transition, a stopping point in a long cultural journey where new values must be learned and some old ones shed.

For the displaced refugees from Southeast Asia, the senior prom last weekend had little meaning. Auditioning for a part in the school production of "Mame" last winter was unthinkable -- perhaps incomprehensible -- for students whose customs were grounded in distant cultures. What did it feel like to try to adjust to Blair for a girl from Latin America, raised in the most strict and upright Catholic tradition of her home country, whose parents refused to allow after-school social activities, such as a school dance? And what was it like, as an avid soccer player in one's homeland, to arrive at Blair and sign up for a gym class in "football," only to find out later that the sport involved touchdowns and huddles and an oblong ball.

For the most part the foreigners' feelings and political concerns remain a mystery to their American classmates, who know them mainly because of the cacophony of foreign words and phrases that are always audible along one of the A building corridors. But can an American student comprehend why two Cambodians, one with allegiances to the Khmer Rouge, the other to the Pol Pot regime, will not sit next to each other in a history class?

Academically, Blair administrators face the problem of placing non-English speakers at the proper course level. Does a seventh-grade education in Thailand parallel seventh-grade here? Where do you place a Lebanese math wizard whose fluency in algebra is greater than his fluency in English?

Some of the foreign-born students need little help -- the valedictorian of this year's graduating class was a Vietnamese, Hao Quang Vu.

Five faculty members teach English for speakers of another language (called ESOL), using Vietnamese and Spanish as a base for such subjects as history, math, science and electronics. The ESOL classrooms have strikingly similar decors: English words in large type -- such as wall, clock, door, window, chair, desk, blackboard, book -- are in relevant places. "Columbus sailed from Spain in 1492," is written in chalk on a blackboard at the front of the room. Names on the honor roll sound like telephone listings for the United Nations: Minasso, Jorge, Angel Cruz, Koon Lee, Oleg, Olga, Lim and Koo.

The largest bloc of foreigners come from Latin America and speak Spanish (although Vietnam, with 59 students at Blair, has the largest representation of any single foreign nation). Administrators say the Hispanic students, although comforted by their numbers, have had greater problems adjusting to Blair because with so many peers who speak their language there is less incentive for them to learn English.

In an office on the main floor in the A building, across from the school store, assistant principal Mary Curry and secretaries Louise Neam and Alice Matthews hold forth in the attendance office. On the wall are senior class pictures from earlier eras: the 949 members of the Class of '65, the largest in Blair history, sit perfectly erect with their caps in parallel tilts; the bare-headed members of the class of '81 are noticeably less symmetrical.

Curry, Neam and Matthews are in a typical pose: They motion deliberately with their hands and speak in loud, emphatic syllables. The problem is communication.

The attendance office is a constant crush of students asking questions and needing answers in foreign tongues. The school's guidance counselors are not equipped to deal with the dozens of foreign languages other than Vietnamese and Spanish, so the solution often lies with foreign students who have lived in the U.S. for a few years. Curry and Neam recruit them to serve as translators who can phone non-English speaking parents, explain school matters to students and relay messages to teachers.

Lourdes Cede, a guidance counselor who is bilingual in Spanish and English, counsels many Hispanic students whose families impose a strict moral code that often forbids activities that are routine for most Americans, such as going to a school dance. Often she is the only link between two conflicting cultures, phoning parents to explain that a dance is "safe" and that movies are part of the American teen-ager's diet.

Despite efforts by students and teachers to encourage the notion that socio-economic and ethnic diversity is Blair's greatest strength -- rather than its weakness, as the school's detractors frequently charge --there are inevitable tensions and problems that result because of it.

And it is the problems associated with the school's diversity -- which outsiders have expanded by mythical proportions -- that are the root of the current political debate over Blair High's future.

Minor racial friction surfaced among the black and white cocaptains of the pompon squad this year. Some blacks felt excluded by the Boys' Service Club and by a clique of girls nicknamed the clan (some suggested, cynically, that the white students picked the name to imply Ku Klux Klan. The students denied this).

A non-English speaking Asian student, complaining of constant harassment by a group of Americans, vented his frustration (successfully) by leveling a karate-style kick to a native's midsection.

There is the recurring administrative problem, seemingly simple on the surface, of deciding what kind of music (rock? soul? reggae? new wave? punk? disco?) to play at a school dance.

And there is a middle group at Blair -- the so-called average American students, black and white, -- that some administrators fear has been left out of the equation because of the commitment of resources for foreign and remedial students. Academically inclined students have felt shortchanged, too, because the school can provide only one period a day for some advanced placement courses.

School system officials who are critical of Blair have pointed to the school's comparatively low test scores to try to show that the school has academic problems.

Although in the past students and teachers suffered from the stereotype that the school was bad, now they focus on a newly aroused school spirit. With the arrival of 35-year-old Joseph Villani as principal in 1980 Blair had a turn-around. Students now cite each other for littering, and the once-papered hallways have been transformed into almost spotless corridors. The school band, which dwindled to 15 members two years ago, revived into an earthy 75-member group under the direction of Ray Harry, the new band leader, who was band president at Florida A & M when he was a student there. The yearbook, Silverlogue, a victim of apathy for several years, took the challenging and positive theme in 1981 of "diversity." This year the theme was "success."

The faculty and administration are vocal partisans, offering constant reminders that Blair has had far fewer racial problems recently than schools elsewhere in Montgomery County. And they emphasize that despite lower test scores overall, Blair's top students compete academically with the best at the county's other 21 high schools.

Administrators and parents reject outside suggestions that students from the predominantly black Maple Avnue area give Blair a ghetto school identity. Many Maple Avenue students have been leaders at Blair. Sandra Gray, president of this year's junior class, and Paul Long, who will succeed her as president of next year's senior class, both live on Maple Avenue. So does Keith (Anwar) Gilbert, a linebacker on the football team who has worked as an aide in the school attendance office. Anwar said yesterday that he never has been in trouble. He said that when he earlier told a reporter that he had never been in jail for "very long," he meant that the only time he has been at a police station was for questioning about activities of other people.

The school's biggest morale boost came on Jan. 14, 1981, when singer-composer Stevie Wonder made an impromptu visit to Blair before leading a birthday march and celebration in honor of the late civil rights leader, Martin Luther King, Jr., in downtown Washington. The theme of Wonder's "campaign for world happiness" was not lost on the students. He picked the school as a stopping point because of its racial and ethnic mix.

"You are very, very fortunate in that, in essence, this school is a melting pot of many different people and many different cultures," Wonder told the students during a 45-minute assembly.

"You are in a unique position, because you have a chance to really bring it together. Together, we can make the difference that we need in the world for the essence of peace, unity, brotherhood, and equality to happen."

A photograph of Stevie Wonder now hangs in the principal's office.