Washington leaders, including Mayor Marion Barry, yesterday mourned the death of D.C. Board of Education member Edna Frazier- Cromwell and praised her for "doing so much" in her three years on the board.

Barry said in a written statement that Frazier-Cromwell, 50, who died of cancer Sunday morning at her home, "was a person who cared tremendously about her community and her fellow citizens, even though she went through so much personal suffering over the past months."

Frazier-Cromwell, a librarian and researcher, was known as a quiet but tough and efficient board member who worked to institute competence testing for new teachers, adopt a new standardized test for students and reduce teacher absenteeism. She kept her illness a private matter for months but recently became very weak and incapable of getting around without a wheelchair, according to several board members.

School board President R. David Hall said Frazier-Cromwell "fought till the end to make improvements in the system." A picture of her on a wall outside the school board meeting room was draped in black yesterday.

"She had planned to finish her term and name a successor," her husband Oliver Cromwell said yesterday. "She didn't expect that [her strength would dissipate] so soon," Cromwell said.

Frazier-Cromwell, who was born in Knoxville, Tenn., and attended high school and college in the District, became known as a civic activist when she organized her neighbors to try to combat the increase of drugs and crime in their community around 14th and U streets NW, one of the city's most notorious narcotics centers.

She was appointed to the board in 1983 to represent Ward 1, in the heart of the city. She succeeded Frank Smith Jr., who resigned after he won a City Council seat. In November of that year she won election to the board in her own right.

Smith praised her as a "diligent public servant."

Serving on the school board "was an extension of her commitment to the community," said Ibrahim Mumin, chairman of the Shaw Coalition Redevelopment Corp., which has received the rights to develop six city-owned properties in the Shaw area.

"She felt that the problems in the community were widespread and required a comprehensive solution that encompassed economic reform and educational reform and social change," Mumin said. "She will be greatly missed."

Hall said the board must appoint a new representative for Ward 1 until the November election, when a successor will be selected by the ward's voters. But Hall recalled that the board had difficulty filling the seat in 1983 and noted that some members favor changing board rules to allow a seat to remain vacant until an election.