The D.C. school board yesterday elected newcomer David H. Eaton as its president, signaling the emergence of a slim new majority of six board members elected since the city's divisive 23-day teachers' strike in 1979, which many believe showed the school board at its most fractious.

Eaton, 49, who is D.C. Mayor Marion Barry's pastor and longtime personal friend, defeated incumbent president Eugene Kinlow through the support of two other newly elected board members--R. David Hall (Ward 2) and Wanda Washburn (Ward 3)--along with three incumbents Barry helped elect in 1979, Nathaniel Bush (Ward 7), Linda W. Cropp (Ward 4) and Frank Smith Jr. (Ward 1). Bush was elected the board's vice president.

The vote, which the winning side hailed as a step toward bringing harmony to the board, gave Barry more potential allies on the board than he has had during his tenure as mayor. Following the bitter strike, Barry, a former school board president, declared that it was time to sweep some of the more contentious members off the board.

Eaton said following his victory that the board now appears divided into two groups, "people who feel as though the stress ought to be on getting a good superintendent and supporting him or her, and another group which believes in daily involvement in the schools." He put himself and his five supporters in the former group.

But the slim 6-to-5 margin and the immediate sharp criticism Eaton's election drew from opponents seemed to promise difficulty in bringing peace to the board. The vote further isolated the four board members whose terms preceded the strike, Barbara Lett Simmons (At-large), R. Calvin Lockridge (Ward 8), John E. Warren (Ward 6) and Bettie G. Benjamin (Ward 5).

Lockridge, Simmons and Warren were strongly identified with the board faction that was blamed for driving popular former schools superintendent Vincent E. Reed from office in 1980. In addition, none of the three initially supported Reed's successor, Floretta D. McKenzie.

Before yesterday's vote at Shaw Junior High School, Lockridge, a former board president, said Eaton's inexperience will "set back progress of the board six months to a year." Newcomers, he said, "would have difficulty finding their way to the bathroom," let alone figuring out answers to complex school problems such as declining enrollments and shrinking budgets.

Simmons charged that Eaton had failed to attend any meetings of the board or its committees, saying he has shown "no evidence" of leadership or deep concern for education.

But Eaton--senior minister of All Souls Church at 16th and Harvard streets NW, and a former dean at Federal City College and at Howard University--said he was a "fast learner," and called upon the board for its help. In a later interview, Eaton said he did not seek the board presidency until he was urged to do so by about 30 citizens and three incumbent board members.

Smith, a strong Eaton supporter, said that he and other board members believed Kinlow should be replaced because he had not been an effective enough "drum major" in winning public and financial support for the schools, and because Kinlow had failed to make peace among the board members.

Smith said Kinlow's appointment of Lockridge as chairman of the board's finance committee, for example, had resulted in a "bellicose, strident, confrontational style" that he called Lockridge's hallmark.

Following his defeat, Kinlow said he regretted that "the cohesion I dreamed about did not occur last year." He and Eaton embraced warmly after the vote. In winning election last year, Kinlow received the five votes he got yesterday, plus that of Alaire B. Rieffel, defeated by Hall in November.

Kinlow, who also won election with Barry's support but has recently clashed with the mayor over the schools' budget, said that Barry may now believe he has control over the board. "But we will see," he added.

Eaton brushed off insinuations by his opponents that he would be a rubber stamp for Barry. He said he expects to differ with Barry on some school issues, especially finances. His priorities, he said, would be stabilizing the schools' finances and working the bugs out of new, stiff promotional standards.

Lockridge and Simmons rejected the notion that the four holdover board members would now be an ineffectual minority faction. "We're not people who can be isolated," said Lockridge. Simmons said she is accustomed to being on the losing end of votes. She said she hoped Eaton and his supporters would not consistently vote as a bloc. "I would hope they will vote what is best for the children," she said.

Yesterday's vote followed installation ceremonies attended by nearly 700 people. At the ceremony, board members and McKenzie celebrated last November's crushing defeat of the education tax credit initiative, which city officials had said would benefit private institutions at the expense of public schools. McKenzie said the margin of opposition to that measure has shown that "education of young people is still the priority of our community."