AFTER ONE of their -- by now-- familiar performances, complete with bickering, race-baiting and parliamentary games, the smallest minds of the District of Columbia School Board have struck another blow for mediocrity: they have rejected Superintendent Vincent R. Reed's dream of a model high school that would offer students from any corner of the city a concentrated opportunity at a first-class, college-preparatory education. Coming as it does in the midst of severe and disruptive teacher layoffs throughout the system, the board's dismissal of Dr. Reed's proposal is all the more depressing -- another example of its petty politics stifling serious educational effects.

Instead of experimenting with an academically rigorous curriculum in a new school setting that could lead to educational improvements throughout the city's high school classrooms, a school board majority of six members dredged up a garbage-pailful of misleading interpretations, personal insults and appeals to increased intracity tensions and succeeded in killing the idea -- thus reversing the board's vote in February that gave preliminary approval for the plan.

Two board members who initially voted for the new school abandoned it this time: Frank Shaffer-Corona, true to form, deserted with a volley of insults directed at two supporters of the proposal, and Nathaniel Bush said that, while he likes the comcept, "we cannot dance a helter-skelter jig to the cracking whip of pubic opinion and pubic opinon-makers." Through Superintendent Reed has been gathering informtion on this proposal for years, Mr. Bush doesn't accept "clever assertions that the proposed school will not cost any additional money"; and he has a list of other questions for further study.

Another opponent, Eugene Kinlow, fed the false impression that Superintendent Reed's proposed school amounts to a prep school for an exclusive elite segment of Washington and that it somehow would rob "the masses." Dr. Reed, in voicing his disappointment at the defeat, said that "there's no way possible anyone could say this school would serve white students only. I could take every white child in the city and I still couldn't fill two classrooms. This system is 97 percent black."

And so long as it is in the hands of a band of self-indulgent politicians, Washingotn's public school system will continue to limit the horizons of those children who are without the means to turn elsewhere for a first-class education. That is the tragedy of this school board. It is also the most compelling reason to join Dr. Reed in renewed efforts to offer the best possible academic training for any child in this city.