An elementary school program intended to make youngsters bilingual by the time they reach the sixth grade has captured the interest of parents here, leading both rich and poor to bus their children to schools as much as hours away.

The program, which totally immerses kindergarteners and first graders in Spanish, and partially immerses second through sixth graders in the language, has nearly 650 enrollees. The only requirement is that the child's native language be English.

The parents come from every economic level and a wide variety of ethnic groups.

"We have the range," said Hal Wingard, a curriculum specialist for the city school district who engineered the inter-cultural language program here. "We have people who are on welfare and people who could buy the city. We have some very influential people and some who find it hard to survive."

While the program was not conceived as a desegregation tool, that is wht it has become.

A court mandate ordering the district to integrate this year was what got the language program rolling. Before that, it has had been on a back burner for lack of money.

The court order was the key to the diverse enrollment. Without it, Wingard guessed, the program might have attracted mostly whites. "There probably would have been no busing, and the sites would have been located differently," he said.

The two project sites are in different parts of the city, one a predominantly white area, the other heavily populated by blacks and Hispanic. The latter school, Oak Park, was on its way to becoming racially isolated, while Longfellow was rapidly shrinking in enrollment and in danger of closing. The program gave new life to Longfellow and ethnic balance to Oak Park.

But most importantly, it showed the pull a voluntary desegregation program can have.

"If you want to achieve successful busing, offer programs worth busing to," said sheila Oberst, one of two women who supervise 20 bilingual teachers.

Oberst said parent interest in the program is "phenomenal."

The reasons are several. Ann Gary, president of the Longfellow PTA, admitted that one is "a kind of snob appeal." Bilingualism, she said, is regarded as a mark of an educated person.

The language program is patterned on one begun more than a decade ago in Montreal. There are similar programs in other parts of the United States - Milwaukee offers German, Silve Spring, Md. (Four Corners Elementary School) French, and Culver City, Calif., Spanish - but none, said Wingard, has a program as large as San Diego's.

Only Spanish is spoken in kindergarten and first grade classrooms. In the second through sixth grades, half the subjects are taught in Spanish, half in English. Those taught in Spanish vary from grade to grade, Oak Park principal Dan Wilson explained, so it cannot be charged that "easier" subjects are taught in the foreign language.

The district intends to expand the immersion program next year, all the way through the twelfth grade. It is thinking, too, of introducing a third language at fifth grade level, on the premise that once a second language is learned, a third is easier to pick up.

While some white parents listed the desire for an integrated experience among the reasons for sending their children to the program, black parents said this was not their concern.

"That was nowhere in my mind," ernestine Johnson said, but language and cultural awareness were. She wanted her 6-year-old, who spends more than two hours a day on a bus, "to be able to communicate with the Spanish people in the neighborhood."

Arthur Dungee echoed her view. "I have never even considered the integration part," said Dungee, a black parent with twin boys in the second grade. Mastery of a language, particularly Spanish, he said, was his primary interest. Already his children "get along better" with Spanish-speaking kids in the neighborhood, he said: "when they go out into the world, they will run into more."

Dr. Harry Bluestein, a faculty member at the University of Califarnio Medical School here, and his wife, Eleanor, bus their children from the wealthy la Jolla area both for the opportunity to become fluent and to mix with other races. They are looking forward to the district's promised Spanish program for parents.

Carl Engstrom, an attorney and realtor, buses his two boys to Longfellow. A foreign language is a very necessary part of a quality education," he said. "It's important it commences at an early age without the impediment of an accent."