D.C. mayoral candidate Patricia Roberts Harris is scheduled to be the keynote speaker at six high school graduations next month, giving her exposure to nearly half the school system's graduating seniors, their families and friends--and about half as many as Mayor Marion Barry may have access to.

Barry, who is seeking reelection, wants to give out a newly created Mayor's Achievement Award to the valedictorians and salutatorians at all high school graduations.

The mix of pomp, circumstance and politics has upset schools Superintendent Floretta D. McKenzie, who, according to several of her staff members, fears the commencements will become a political showcase.

The scheduled speeches by Harris also have generated complaints from various school administrators, school board members and parents.

"I don't think it's just coincidental that a candidate that has had so little to do with educational issues in this city in the past should suddenly emerge" as the most sought-after graduation speaker, said William H. L. Brown, president of the D.C. Congress of Parents and Teachers, referring to Harris.

Brown said he thought Barry's decision to give out awards this year is "a political ploy, too . . . . We're not fools."

No other candidates for mayor have been asked to address high school commencements.

Board member R. David Hall (Ward 2) said, "I don't think the graduations should be a political thing. I would be very concerned if there is some kind of chicanery here."

Hall suggested that board member R. Calvin Lockridge (Ward 8) may have arranged the abundance of Harris speeches. But Lockridge, who wears a large orange-and-black Harris-for-mayor button wherever he goes, says he played no such role.

"I think this just shows who the students think the role models are," Lockridge said. He said he thought Barry is "fortunate to be speaking at any graduations after the damage he's done to the schools."

Patricia Miner, Barry's liaison to the public schools, said Barry decided months ago to initiate an award to praise achievement. Last year, she said, he sent letters to all the valedictorians and salutatorians.

Miner added that Barry may not be able to present all of the awards personally because of his schedule.

McKenzie has declined to comment publicly on the matter. But her office recently directed all high school principals to give an account of how graduation speakers were selected.

She also sent a memo to all schools, warning employes that they are not to engage in any politicking "while on duty" or "use their position in the D.C. public schools to promote a political position."

Most of the principals told McKenzie that the graduating seniors themselves chose Harris as their speaker, according to Janis Cromer, spokeswoman for the schools.

At McKinley High School in Northeast, one of those at which Harris is scheduled to speak, assistant superintendent P. Gary Freeman said Harris was the students' second choice after Rep. Shirley Chisholm (D-N.Y.), who was not available.

Freeman said he has been assured that Harris will not give a political speech. "Of course," he added, "the fact that she's there makes it political."

Isaac Jackson, vice principal of McKinley, said some parents have called the school to complain about the scheduled speech by Harris.

Harris is scheduled to speak before 2,500 students at commencements at Coolidge, Ballou, Anacostia, McKinley and School Without Walls as well as five of the city's vocational high schools. There are 5,751 graduating seniors this year.

Jacqueline Casselberry-King, Harris' press secretary, said the candidate, a Cabinet member in the Carter administration, receives numerous speaking requests from schools. She said Harris will stick to educational issues in her commencement addresses.

"Mrs. Harris has been locally and nationally known for years," the press secretary said. "She is a role model."

Barry said Saturday that he does not object to Harris speaking before the graduates. But, he said, "a number of parents have asked me the question, 'Where has she been all this time on educational issues? Where was she on the tuition tax credit?' "

Barry said he has not made "any overt efforts" to be the main speaker at any of the graduations. "I don't think people should use the schools to politicize things," he said. "There will be plenty of [candidate] forums."