At least 30 candidates, including former pricipals and teachers, parent activists, counselors and D.C. Mayor Marion Barry's pastor, filed by yesterday's deadline for two at-large and three ward seats on the D.C. school board that are being contested in the Nov. 3 election.

The most competitive of the races will be for the two at-large positions, currently held by Frank Shaffer-Corona and Barbara Lett Simmons, both of whom are seeking reelection.

Eighteen candidates are seeking those two seats, including the Rev. David Eaton, a well-known cummunity activist, friend and pastor of the mayor; Athel Q. Liggins, the former principal of McKinley High School in Northeast Washington; Frank Bolden, the retired athletic director for the D.C. public school system, and Phyllis Young, who helped lead the parents' fight for increased school funding this year.

There also is expected to be a lively race in Ward 8, where six candidates are running against the outspoken and often-controversial incumbent, R. Calvin Lockridge. Among those opposing Lockridge's reelection bid are Phinis Jones, former aide to Ward 8 City Council member Wilhelmina Rolark; Advisory Neighborhood Commissioner Linda Moody and management consultant Gordon A. White.

The Ward 3 race will pit two well-known community activists, Wanda Washburn, former president of both the Deal Junior High School and Wilson High School parent-teacher associations, and Mary Ann Keefe, who is active in the Democratic Party here and was citywise cochairman of Sen. Edward M. Kennedy's presidential campaign in 1980. Carol Schwartz, the current Ward 3 board member, declined to seek reelection.

There are three candidates in Ward 2: incumbent Alaire B. Rieffel; Marjorie Maceda, a teacher in a parochieal school and president of the Amidon Elementary School PTA, and R. David Hall, the founder of the D.C. Street Academy, a school for former dropouts.

All the candidates filed the required petitions with signatures of registered voters at the city's Board of Elections and Ethics. The elections board now will review the petitions to determine if the signatures are of valid voters and will entertain any challenges before placing the candidate's names on the ballot.

Some persons involved in city politics said they thought the unusually large number of candidates, especially for the at-large seats, might split the vote and thus work to the advantage of the incumbents. This could also happen in Ward 8, they said, which traditionally has had a low voter turnout.

In the highly competitive at-large race, Shaffer-Corona generally is considered to be the weaker of the two incumbents as a result of his controversial stands and frequent verbal skirmishes with other board members. Shaffer-Corona is the only board member whose conduct has ever been formally censured by the board.

The board took that action last year after Shaffer-Corona charged the school system for $1,900 worth of phone calls to Iran that he made in an unsuccessful, personally inspired effort to get the American hostages released. He also provoked the ire of his colleaugues two years earlier when he charged the school system for a trip he made to Cuba.

Two Hispanics, Andrea Gonzalez and Manuel B. Lopez, are running for Shaffer-Corona's seat.

The large number of at-large candidates, said one District Building political insider, "means that there are a lot of people who are interested in the schol board and making good things happen, or there are other people who see it as a political springboard."

But some candidates, Simmons said, may have been attracted by the relatively high salaries the board members receive. Board member4s currently are paid $19,656 and the board president $22,152, but their salaries could increase next year.

Barry, who supported four candidates, all winners, in the last school board election, generally does not intend to get involved in the election this time, although he may endorse Eaton, according to Patricia Miner, Barry's liaison to the school system.

However, a new committee has been formed by several prominent D.C. residents, including Schwartz and former school superintendent Vincent E. Reed, to screen and evaluate school board candidates.

The campaign is likely to center on a few major issues, including the school system's shrinking resources and the board's reputation for in-fighting and its past conflicts with school administrators.

Following are the names of other candidates who had filed by last night for at-large seats: Trummie Cain, Angie Corley, Ernest Mercer, James Carter Jr., the Rev. Katherine Bailey Moore, Charlotte Holmes, Dot Cresswell, Berlene Newhouse and Edwin C. Parker.

Other candidates who filed for the Ward 8 seat are: O.V. Johnson, Absalom F. Jordan and Edward H. Moore.