District of Columbia Public School Superintendent Floretta McKenzie's announcement that she will resign next year has generated an outpouring of praise for a job well done since she took over in 1981.

But something is woefully out of whack when a city can keep the same mayor for eight years, but turns over eight school superintendents in 12 years and then loses one of the best it has ever had after just six.

What is it about running the D.C. school system that chews up superintendents faster than running the city would burn out a mayor?

In an interview with reporters last month, the 52-year-old McKenzie declared: "I love the city. I love the school staff. I love what I'm doing. But I have been here six years and I just think it's time to move on and give someone else a chance." Conspicuously absent from her love list was the D.C. school board.

And therein lies the rub.

Early this year, for the first time during her tenure, board members criticized McKenzie to her face at a private breakfast. One member said he was frustrated because some schools were not improving fast enough. Another complained about inadequate top managers. Still another wondered whether the school administration was inflating test scores, and told McKenzie to get rid of "bumbling administrators" and generally to clean up her act.

McKenzie, according to reports, was reduced to sobs.

This was the thanks she received for continuing an era of stability, pride and classroom accomplishment, not to mention a remarkable partnership between the schools and local businesses.

Among the school board's most far-reaching power plays, however, was its ability to wrest control of approving high school principals from the superintendent.

Nowadays, rather than answer to the superintendent, principals are more likely to be niggled by school board members, who are lay people with political ambitions that sometimes take precedence over educational concerns.

Notice, for instance, how many schoolteachers will call in sick during the upcoming school board election so they can work the polls for the incumbent candidates to whom their principals are indebted.

A major structural change in the D.C. school system occurred under Floretta McKenzie that weakened not only her authority but that of the superintendent who will follow her.

Little wonder that when McKenzie ordered Woodrow Wilson High School Principal Michael Durso to reinstate a student accused of rape, he confidently refused. Not only did Durso get away with this act of insubordination with a mere slap on the wrist (a brief suspension instead of firing), he came out of the fray with honors -- being named the city's best high school principal by his peers.

Although McKenzie's resignation comes with more grace than many other departing superintendents, the same fundamental problem between the superintendent and the school board has plagued the school system for years, and appears to be worsening.

For the first five years of McKenzie's tenure, District students' standardized test scores were improving steadily. Then McKenzie made the decision to change the tests, to make them harder.

Suddenly, reading and math scores fell below national norms in all grades tested except for mathematics in the third and sixth grades. The elementary pupils' reading scores were just slightly below the national norms. But the scores for 11th graders were two years below the norm in reading and 1.8 years below the norm in math.

McKenzie, for all her talents, had never been a high school principal and did not come up through the D.C. school system. Thus, school board members were able to spend six years sharpening their teeth on her and now appear poised to tear into her successor in ways this city has not seen in nearly a decade.