THE YEAR 1975 WAS A TUMULTUOUS ONE FOR the District school system. After months of warfare, factions on the school board were still embroiled in a bitter dispute over the performance of the superintendent, a brilliant but controversial educator from Chicago named Barbara Sizemore.

Sizemore had become D.C. school superintendent in October 1973, the first black woman to head a major city school system. She was selected for the job over 98 other applicants. But barely two years later, on Oct. 9, 1975, Sizemore -- accused of being an inept adminstrator and unreliable employe -- was fired.

At the time of board hearings leading to her dismissal, Sizemore's detractors complained that she often defied the elected school board and spent more time organizing disruptions of board meetings than meeting administrative deadlines. Sizemore has never seen it that way.

"I think any superintendency has to be understood from the standpoint that Washington is a colony, and I think everything else is impacted by that -- certainly the school board," Sizemore, 59, said recently.

After nearly pulling off a political upset when she ran for the city council in 1977, Sizemore left town to take a job as a professor at the University of Pittsburgh's department of black community education, research and development. She has been there ever since and says she's found the niche in Pittsburgh denied her in D.C.

Her ouster, Sizemore is convinced, came about because "white-controlled black politicians" felt she was a threat to the Washington establishment. She reserves some of her strongest criticism for the white-owned media, especially The Washington Post. And she says home rule, which arrived during her superintendency, is an illusion.

"Home rule is just an attempt to keep the majority black community under control," she said. "It's given the people the impression they have power when they don't. And The Post, which wields disproportionate influence in this leadership vacuum, is part of that big farce."

In Pittsburgh, Sizemore teaches and does research, "identifying practices which result in high achievement by Afro-American students." She has written a book on her experiences in the D.C. school system -- The Ruptured Diamond, published by University Press of America in 1983 -- and is working on a couple others. One will examine the success of three predominantly black, high-achieving elementary schools in Pittsburgh. The other, co-authored with Howard University's Nancy L. Arnez, will focus on the role of black school superintendents.

Interestingly, in 1979, Sizemore married Jake Milliones, assistant professor of psychiatry and psychology at the University of Pittsburgh's Western Psychiatric Institute and Clinic . . . and president of the Pittsburgh school board.