The federal government's role in bilingual education, which Education Secretary William J. Bennett has just proposed changing, has rested on three pillars. They have alternated between using the carrot of federal aid and the big stick of the law to persuade, and then force, local school districts to provide special services to children who speak only limited English.

The three are Title VI of the 1964 Civil Rights Act, Title VII of the Elementary and Secondary Education Act of 1968, and a 1974 Supreme Court decision called Lau v. Nichols that pitted Chinese students against the San Francisco Unified School District.

If Bennett has his way, the thrust of all three would shift from a bilingual-only posture to give localities more flexibility in choosing their teaching method. Details, Page A10.

Bilingual education refers to the method of teaching children in their native language, allowing them to make the transition to English gradually. Other methods include English as a Second Language (ESL), in which children take English classes along with other courses, and immersion, which provides intensive studies in English.

Bennett's proposal would require regulatory changes and a change in the law to allow Title VII money in the Elementary and Secondary Education Act to be used for methods other than bilingual education.

But even while restricting his proposal to Title VII money -- which is voluntary federal aid for which local school districts apply -- Bennett's attempt to change the tone of the federal role would also affect the other "pillars," civil rights enforcement and the Lau "guidelines" to school districts.

The impact in those other areas is potentially more significant because, unlike Title VII, they are mandatory, not voluntary.

The Supreme Court, in its Lau decision, never proscribed bilingual education as the only remedy, or even the preferred remedy, to the problem of teaching children who speak limited English. Instead, the court said:

"Teaching English to the students of Chinese ancestry who do not speak the language is one choice. Giving instructions to this group in Chinese is another. There may be others."

But Ford administration education officials used the Lau decision to force hundreds of school districts to sign binding agreements to establish programs for limited-English children, using primarily the bilingual method.

Education Under Secretary Gary Bauer said yesterday that while the Reagan administration has no plans to try to alter these binding agreements, the department might look favorably on any request from local authorities who seek to renegotiate their agreement.

"Clearly, we're sending a message here," Bauer said. "If one of those 500 school districts wants to come back in and renegotiate, we'll be willing to talk to them" about lifting the bilingual-only requirement.

Renegotiating the agreements could open the department to charges that it was reneging on an area of civil rights enforcement. "The one message we don't want to send is that in any way we're lessening the civil rights commitments," Bauer said.

Title VII of the Elementary and Secondary Education Act, also called the Bilingual Education Act, initially was as open-ended as the Supreme Court decision; it contained no language to restrict the use of federal funds for other kinds of language training.

Instead, the act stated:

" . . . It is the policy of the United States to provide financial assistance to local educational agencies to develop and carry out new and imaginative elementary and secondary school programs designed to meet these special educational needs."

But in 1974, under pressure from Hispanic groups, the law was changed to require that children must be taught in their native language for schools to be eligible for any of the federal money, now $139 million annually. Last year, Congress agreed to a compromise, so that 4 percent of the funds could be spent for methods other than bilingual education.

It is that 4 percent cap that Bennett is now seeking to have lifted.