At the age 12, Oscar Salinas is a bright and enthusiastic young man who understands very little of what goes on in his fifth grade class at Barrett Elementary School in Arlington.

The reason is hardly surprising. Oscar, who recently moved here from El Salvador, speaks and understans very little English. He is just beginning the process of assimilation into the American culture. Like millions of immigran children before him, he is going through the process in public schools.

But there is a major difference between the experience of Oscar Salinas in 1979 and those of immigrant children one or two generations ago. For those early immigrants, the process of Americanization and learning to speak English was largely a matter of sink or swim. At Barrett, that attitude has been eliminated.

Each afternoon, Oscar leaves his regular classroom for two hours of intensive English instruction. Oscar is one of more than 150 children at Barrett receiving some kind of special instruction and one of more than 90 children receiving special English instruction.

As much as anything in recent years, education has come to focus on special needs, and nowhere is this more evident than Barrett School. f

There are programs for children with learning disabilities, programs for fast learners and programs in Vietnamese.

For children just learning to speak English, is an intensive program called High Intensity Language Training (HILT). For those more versed in the language but still needing special help, there is English for Speakers of Other Languages (ESOL). In addition, Barrett is a Title VII school, which supports a bilingual, bicultural program in Vietnamese.

Because at least one-third of the children at Barrett come from families with incomes low enough to qualify for reduced price or free lunches, Barrett also is a Title I school, one of 15 in Arlington. That entitles the school to one extra teacher, paid by the federal government, who spends 45 minutes every day tutoring 36 children below their grade level in reading. "The goal is to bring then up to grade level," says the teacher, Kathleen Walter. "It's very slow. You can't give them too much. You just have to work steadily and coordinate what you do with the classroom teacher."

With small groups of children, Walter painstakingly goes through the fundamentals of reading. for some of the children, it is their first experience with vowel and consonant sounds, and they are reading a story about Jake the Snake to become familiar with the long A. Other children, who have a better grasp of the fundamentals, are working to improve their comprehension.

For children in the Vietnamese program, the work is even more fundamental.

Vu Thi Dung, a former nutrition specialist for the Catholic Relief Service in Vietnam, directs the program for the Arlington schools. She is based at Barrett because it has 44 Vietnamese children, more than any other Arlington School. "A lot of parents want their children to keep the Vietnamese language, but at the same time they want their children to be like Americans. They want them to learn English fast," says Dung, who came to the United States in 1972.

Three times a week for 30 minutes, Vu Thi Kim Phan, an instructional aide in the program, sits down at a table in a small basement room with Toan Tran and Thao Lam, two 7-year-old Vietnamese children who speak very little English.

Phan's assignment is to explain, in Vietnamese, basic concepts the children have been unable to grasp from their classroom teacher because of their limited English.

A few weeks ago, Phan was explaining the concept of top and bottom, which they had failed to understand when their second grade teacher was explaining it in English. Later, Phan helped the two children with basic computations in addition and how to tell time.

Principle Lionel Seitzer estimates that 40 percent of the 401 children at Barrett come from families where a language other than English is spoken. Vietnamese, Spanish and Korean are the main languages.

For the 91 students in his school who are enrolled in special English and bilingual programs, he says, the goal is fluency in English as soon as possible.

"Our program is a transition program," he says. "It is not a maintenance program and it is not an enrichment program. As soon as the children can function in English, they will be phased out of the program."

Barret children who are native speakers of languages other than English will receive the bulk of their English training from Blythe Owens Bisbee, a former Peace Corps volunteer who runs the ESOL and the HILT programs.

In the mornings, Bisbee works with groups of 10 to 12 children who have picked up the fundamentals of English.

"They can say a lot and they can hear a lot, but when you pin them down, they can't say things correctly," says Bisbee. "Most of these children, when they leave school, don't speak or hear English at home."

In the afternoons, she spends two hours and 15 minutes with another group of children who are just beginning to learn the language. Oscar Salinas is in that group, along with 16 children from Cambodia, Colombia, India, Korea, Peru, Turkey, Taiwan and Vietnam.

Rencently, they were working on vowel sounds.

Holding a picture, Bisbee would say, "A dog's hand is a?"

"Paw," the children would answer.

"I am building a house. I have a?"

"Saw."

Despite the language barrier, most of the children blend in quickly with their American classmates.

Virith Kho, orginially from Cambodia, speaks virtually no English and his teacher is not even sure if he ever attended school before. Yet 11-year-old Virith has managed to pick up the game of kickball -- a version of baseball where the ball is kicked instead of batted.

When Oscar Salinas really has to comprehend something well, a classmate, Monica Avalos, translates into Spanish for him. Monica came here from Guatemala several years ago, and Barrett is the third U.S. school she has attended. Although Monica speaks English fluently, she has never been in one of Barrett's language programs. "I learned English just by hearing people talk," she says.

Bisbee predicts that most of the children will have a working knowledge of english in about a year, and that the process of assimilation will follow very quickly.

"This is the melting pot, and these children are very much into the melting-pot philosophy. If they have foreign names with accents on them, they quickly drop the accents because American children do not have accents on their names. They want to be Americans."

As Oscar Salinas says, through his interpreter Monica, "I want to grow up in America and work here and learn to speak English. I will work very hard and do my best."