Ruth B. Spencer, 90, a teacher and community activist who served on the D.C. Board of Education during one of the most contentious times in public school history, died Aug. 28 of pneumonia at Laurel Regional Hospital. She had lived in Silver Spring since 1982.

Mrs. Spencer was appointed to the Board of Education in 1956, two years after the U.S. Supreme Court's Brown v. Board of Education ruling that segregation in the nation's public schools was unconstitutional. She was one of three African Americans and three women appointed to the nine-member board by judges overseeing the District.

"The people who got her on the board wanted her to be quiet," her daughter, Judy Spencer, recalled in a phone interview, "but she wasn't going to do that. She had to fight a lot of battles with the powers that be, white and black. She was constantly fighting those battles for the kids."

A tiny woman, barely five feet tall and never weighing more than a hundred pounds, Ruth Spencer was "astute at reading the situation and knowing what needed to be said in any given situation," her daughter said, "but she could be a holy terror when she had to be."

As a former teacher, the first in several years to serve on the board, she jumped into the fray immediately. In her first speech, she said she found it shocking that some District schools were keeping records according to race, in violation of board policy. "I want some answers," she said.

Later, she urged the board to adopt a blueprint that would establish uniform standards and teaching methods.

In a 1957 speech at Howard University, she warned against "the naive tendency to assume that desegregation automatically establishes integration" in the schools. Schools, she said, were involved in an "uncomfortable transition period to dispel racial myths."

After four years on the board, the work, the pressure, the occasional threats and the demands on her time got to be overwhelming. She collapsed from a bleeding ulcer and resigned a few weeks later.

Ruth Spencer was born in Washington and graduated from Dunbar Senior High School. She received a bachelor's degree in liberal arts and a master's degree in history, both from Howard University, and did postgraduate work in school guidance at Catholic University.

In 1937, she began teaching American history and world history at Bates High School in Annapolis. During her three years in the classroom, she introduced the study of black history into the curriculum.

She became a guidance counselor in 1941 and immediately tackled the school's rising dropout rate. She approached businesses for assistance in establishing a work-study program that would allow students to stay in school, even as they worked to help support their families. Despite opposition from some white business owners in segregated Annapolis, she was able to get the program running. She ended her tenure at Bates as vice principal.

In 1943, she married Adna L. Spencer, a dentist and fellow Howard alumnus, and she retired from teaching in 1945. For the next two decades, she was involved in civic and public service activities.

One of the most satisfying of her community service endeavors was the Baker's Dozen Youth Center. The Baker's Dozen -- Mrs. Spencer and 12 of her Delta Sigma Theta sorority sisters -- recognized that in the mid-1940s, the Shaw neighborhood in the 2nd Precinct had the city's highest juvenile delinquency rate. They resolved to establish a center in the area that would meet the needs of young people.

With fundraising schemes that included concerts by Duke Ellington and by Woody Herman and the King Cole Trio (tickets $1.20), the Baker's Dozen purchased two tenement houses and opened the center in 1950. It included after-school tutoring programs, a psychologist, an athletic program and other services. It stayed in operation until 1962.

Mrs. Spencer also was involved in early discussions that resulted in the creation of the University of District Columbia.

In the mid-1960s, she joined the Justice Department's Community Relations Service, an agency created by the 1964 Civil Rights Act to help communities peacefully resolve racial conflict. She regularly worked with human relations commissions across the country before retiring in 1981 as special assistant to the director.

Mrs. Spencer received numerous awards and citations over the years, including a 1959 alumni award from Howard University for "distinguished postgraduate achievement in the field of community affairs." She was a member of Rhema Christian Center Church.

Her husband died in 1979.

Survivors include a son, Richard L. Spencer of Silver Spring; a daughter, Judith E. Spencer of Hyattsville; and a granddaughter.

Ruth Spencer was a schoolteacher, vice principal and guidance counselor in Annapolis before being appointed to the D.C. Board of Education in 1956.Mrs. Spencer also worked in the Department of Justice Community Relations Service.