"Every child in a District of Columbia public school has a right to a highly effective teacher — in every classroom, of every school, of every neighborhood, of every ward, in this City. That is our commitment. Today . . . we take another step toward making that commitment a reality."

That quote is from District of Columbia Schools Chancellor Michelle Rhee, announcing the terminations of 241 teachers on July 23.

What ought to be a routine culling of underperforming employees instead appears to be an event unprecedented in any of this nation's big-city school systems

Rhee disclosed that she had fired 6 percent of her teaching corps. Rhee dismissed 165 teachers who had received poor performance appraisals and 76 who didn't have proper teaching licenses. What's more, Rhee said an additional 737 teachers have been rated minimally effective. They're ineligible for step increases and have one year to improve or lose their jobs. At the outside, then, Washington could remove a total of nearly one-quarter of its 4,000 teachers from the city's classrooms.

Now consider the fate of the good teachers: In June, teachers union members and the D.C. Council agreed on a contract that boosts teachers' salaries by a stunning 21.6 percent. Job security now rests less on seniority protections and more on performance in the classroom. The contract also includes an incentive plan that gives teachers bonuses of $20,000 to $30,000 — annually — if they meet goals that include growth in students' test scores. Note that we referenced "growth" in scores, not "the highest" scores. The pact rewards teachers who help students of any ability level advance — not just teachers whose pupils have the most advantages and do well on tests.

Rhee is a controversial, critics would say bloodless, administrator. Her sole focus is reforming a school system that historically has been among the lowest-performing in the United States. The Washington Post noted in an editorial that there is no joy in knowing the hardships caused for the teachers who've been fired. "But if there is outrage to be felt, it should be directed at a system that has enabled, even rewarded, poor teachers," the Post said. "Consider that in the year Ms. Rhee took over leadership of the schools, only 8 percent of eighth-graders performed on grade level in math, but 95 percent of the teachers were rated as excellent."

For too many decades, too many school systems have tolerated that sort of inverse relationship. If Michelle Rhee leads a revolution of rising expectations, terrific.

Union President George Parker told the Post that Washington's new evaluation system, developed by the district and consultants at Mathematica Policy Research, tries to weed out teachers rather than help them improve. We'll go instead with the Post's retort: Whose children do the critics propose should sit, year after year, in the classrooms of ineffective teachers?

The new D.C. evaluations rely on more than student progress. The protocol includes five 30-minute classroom observations, three by a school administrator and two by an outside "master educator" from the teacher's subject area.

Teachers are scored on 22 variables in nine areas — such factors as classroom presence, time management, and clarity in presenting the objectives of a lesson. Each teacher's overall performance for the year then is converted to a scale of 100 to 400 points. Teachers who score below 175 risk dismissal; those in the 250-to-400 range are judged "effective" or "highly effective."

We don't know if Washington's system is the best, or the best-executed. We do suspect that if every U.S. district took this much care to eliminate its weakest employees, more students would emerge from public schools with educations that qualify them to compete successfully in the 21st century.