Several black leaders, upset about losing Montgomery County's only black school board member to the county executive's staff, have sent letters to the board member and executive.

"The black community and its friends and allies in the white community expended inordinate amounts of human resources and dollar resources to elect you to this [school] board," reads a letter sent to Odessa M. Shannon and signed by several black leaders including Roscoe Nix, president of the local chapter of the NAACP, and many who worked hard on her 1982 campaign.

Shannon announced two weeks ago that she would resign her seat this month to become appointments chief for County Executive Charles W. Gilchrist, the first black woman in the county's history to be appointed to one of the three special assistant posts.

Shannon could not be reached for comment yesterday, but said when she announced her resignation, she thought she could have a "wider impact" in her new $60,000-a-year job. Gilchrist aide Ed Rovner yesterday added that Shannon told Gilchrist she felt confident that her colleagues on the board would select a "kindred spirit."

At least seven blacks are among the 39 applicants who met yesterday's filing deadline for Shannon's seat. The list includes several former school board candidates, one current candidate, the former president of the county-wide Parent-Teacher Assocation, a former president of the Montgomery County school board and former state school board member.

"We believed you when you talked of commitment to all school children and especially to black school children," the letter to Shannon said. "We believed you when you described your dedication and devotion to equal educational opportunity, and your view that equity and excellence must go hand in hand . . . . This is why we do not comprehend your" resignation.

A similar but less personal letter, dated Aug. 30 and signed by nine people, was sent to Gilchrist.

In announcing her resignation from the school board, Shannon said she also would leave her $69,000-a-year job as program director for the U.S. Equal Employment Opportunities Commission. In her new position she will be responsible for appointing county residents to numerous public commissions.

Shannon, a 56-year-old Silver Spring resident, has been considered an eloquent and articulate advocate on the school board for minority students.

"Her decision has really demoralized a number of people," said Hanley Norment, public information officer for the local NAACP chapter and the public relations officer for her school board campaign.

In addition to Norment and Nix, others who signed the two letters were: the two cochairmen of the Citizens' Minority Relations monitoring committee, a former president and vice president of the Montgomery NAACP chapter and the education chairman of the black fraternity Alpha Phi Alpha.

"I am personally angry. I worked [to get her elected] like I had never worked before," Norment added.

In his response to a letter that questioned why he raided the school board of the one county-wide elected black officeholder, Gilchrist responded that he selected Shannon for the "same reasons that the voters selected her."

"She is bright, conscientious and has a constructive and healing approach to problems . . . ," Gilchrist said in a letter to the black leaders to be sent last night. "I would have hoped our years of mutual effort would have prevented indulgences of the theory that there were 'dark and sinister' motives for my action. You should know better."