Lauro F. Cavazos announced his resignation as education secretary yesterday, one day after Chief of Staff John H. Sununu summoned him to the White House and demanded he quit, administration officials said.

The two officials said the White House wanted to have a "stronger" secretary leading the Education Department in the new year and the option of filling the Cabinet slot with one of the Republicans who lost in the November elections. Political observers across the ideological spectrum repeatedly have criticized Cavazos as an ineffective spokesman for education at a time that it has achieved national prominence as a domestic issue.

Cavazos, 63, the first Hispanic Cabinet secretary, offered no explanation in his resignation letter nor any clue about his future plans. He is a former president of Texas Tech University. The resignation was announced at a Cabinet meeting that Cavazos did not attend, and an administration official said he was out of town yesterday.

Deputy Secretary Ted Sanders will become acting secretary after Cavazos's resignation becomes effective Saturday. He plans to deliver a commencement speech Saturday at West Virginia State College in his last official act as secretary, according to spokesman Etta Fielek.

Cavazos was initially appointed by President Ronald Reagan in September 1988 at the urging of fellow Texan and then-Vice President Bush, who reappointed Cavazos after becoming president.

In his letter on the resignation, which was accepted without the usual White House ceremonies, President Bush said: "For more than two years, and under two presidents, you have distinguished yourself through your devotion to improving the education of our nation's children."

Fielek said Cavazos spoke with Bush on the telephone yesterday morning and then faxed a resignation letter to the White House.

"I am especially proud of the contributions I was able to make in expanding choice in education, promoting the executive order on excellence in education for Hispanic Americans, and raising awareness of the growing diversity of America's student population," Cavazos said in the letter.

He became the second official to announce his departure from the Bush Cabinet following the resignation in November of Labor Secretary Elizabeth Hanford Dole to head the American Red Cross.

An administration official said the Cavazos resignation "gives us two Cabinet slots and we've got two candidates for Cabinet slots, so it is a perfect equation." The reference was to Rep. Lynn Martin (R-Ill.), who failed in her challenge to Sen. Paul Simon (D-Ill.), and to Rep. Patricia F. Saiki (R), who lost a Senate bid in Hawaii.

Officials said Martin wanted the labor post and described Sununu as being "enamored" of the idea of Bush making Saiki the first Asian-American to hold a Cabinet post.

Other names being mentioned as a possible successor were Lynne V. Cheney, chairman of the National Endowment for the Humanities; former New Jersey governor Thomas H. Kean (R), now president of Drew University; and former Tennessee governor Lamar Alexander (R), now president of the University of Tennessee.

Cavazos, widely considered likeable but low-key, appeared to suffer from the outset of his appointment from comparisons with the intellectual, combative William J. Bennett, his predecessor as education secretary. A year ago, rumors of Cavazos's imminent departure grew so loud that Bush was moved to publicly restate confidence in him.

Albert Shanker, president of the American Federation of Teachers, responded to the Cavazos resignation yesterday by saying: "Well, he didn't do very much. In fact, he didn't do anything. . . . I'd rather have someone like Bill Bennett, with whom I disagree, someone who has an intelligent point of view and can make a national debate on education issues. That's healthy."

Jeanne Allen, an education analyst at the Heritage Foundation, graded Cavazos "somewhere between a C-minus and a D" because "his tenure has been marked by an underappreciation for keeping education on the front burner of American politics."

Kinder comments came from other observers who disliked Bennett's performance and preferred Cavazos as secretary. "He was, of course, a much desirable alternative" to Bennett, said Rep. William D. Ford (D-Mich.), incoming chairman of the House Education and Labor Committee.

Robert Atwell, president of the American Council on Education, praised Cavazos for his open, cooperative style and said the administration failed to "match his convictions with deeds that would have carried out the commitments implicit in President Bush's desire to be the education president. In that sense, the administration was better served by Secretary Cavazos than he was by those in the White House."