D.C. School Superintendent Floretta D. McKenzie, whose performance has been publicly lauded by most members of the D.C. Board of Education, was given a job rating of slightly above average in a recent confidential evaluation by board members.

The highest possible score that McKenzie could have received was 81, based on a nine-question, nine-point scale. She was rated separately by each board member, and the average of the scores they gave her was 57.

Despite the numerical score, and while there were "areas where improvement should occur," the report concluded that "the total thrust of all comments and evaluation criteria indicated clearly that the superintendent's performance is highly satisfactory."

Board President David Eaton gave McKenzie a rating of 62. He declined to comment on McKenzie's overall evaluation by the board, but said, "In my estimation, I did not give her low marks. I think she's the best superintendent in the country."

The evaluation was based on a scale in which, for each question, a score of 1 through 3 meant below average, 4 through 6 was average, and 7 through 9 was above average. The average score McKenzie received on each question was 6.35.

According to sources, the board members gave her the following scores: Linda Cropp (Ward 4), 81; R. David Hall (Ward 2), 78; Wanda Washburn (Ward 3), 78; Nathaniel Bush (Ward 7), 71; Eaton (at-large), 62; Eugene Kinlow (at-large), 54; Bettie Benjamin (Ward 5), 46; John Warren (Ward 6), 45; Barbara Lett Simmons (at-large), 30, and R. Calvin Lockridge (Ward 8), 27.

Simmons and Lockridge have been among McKenzie's strongest critics on the board. Both declined to comment last night, but six other board members spoke of McKenzie in glowing terms.

McKenzie declined comment on the evaluation results, saying "I don't think it's appropriate. It's a personnel matter and a matter of principle."

Washburn criticized the entire evaluation process yesterday, saying that the results were skewed and did not give an accurate measure of how well McKenzie has performed. "I object to anyone being numerically rated. Those who are out to get anybody will try to deflate the score and those who aren't will have to inflate their scores to compensate. It's all skewed. There is no crisis of leadership in the schools," she said.

The evaluation, based on a letter of understanding McKenzie signed when she took the post in June 1981, ties her job rating to the overall performance of the Washington school system: whether student test scores have improved, whether she has "enhanced the prestige" of the system, strengthened the system's competency-based curriculum, and strongly advocated the board policies to the public.

Several of the evaluation questions were based on those criteria, according to a copy of the form used by board members. Other evaluation questions asked whether McKenzie had kept the board informed on educational issues and alerted them to potential or actual deficiencies in the schools.

McKenzie scored highest (73 out of a possible 81) on the question of whether she extended and strengthened the system's competency-based curriculum and student progress plan. "Each of the above has been accomplished within a timely fashion and in an extremely competent manner," one board member indicated.

McKenzie's worst score (52) came on the question of whether she had improved the accountability and performance of school officers and teachers, in part by developing an accountability system. "The superintendent has performed well but not in an outstanding manner," wrote one board member. "This is an area of needed improvement."

The evaluation is almost a year late. It was supposed to have been conducted after the first year of McKenzie's tenure.

As a prelude to the evaluation, McKenzie gave the board a lengthy report that outlined her accomplishments. In it, McKenzie noted that 80.9 percent of the first- through third-graders were promoted at the half-term this year as opposed to only 68.2 percent the previous year. She said students' comprehensive test and standard achievement test scores rose over the previous year.

If McKenzie had received a below-average rating, according to the terms of her contract, she could have been dismissed, said board officials. The board has not fired a superintendent since Barbara L. Sizemore was dismissed for poor performance in October 1975 on a 7-to-4 vote. Simmons, Benjamin and Warren had opposed Sizemore's firing.