Kansas City, Mo ? The achievement gap between black and white students in the Kansas City public schools has shrunk, a witness testified during a hearing to determine whether court supervision of the district’s desegregation case should end.

But the witness for the school district said Wednesday that part of the reason the gap has shrunk was the loss of some of the district’s lowest-performing black students and top-performing white students to charter schools.

“The probable effect was modest” but was a contributing factor, said Michael Podgursky, chairman of the economics department at the University of Missouri-Columbia.

Podgursky was one of four witnesses testifying before U.S. District Judge Dean Whipple.

The district is asking Whipple to end court supervision of student achievement in the district and dismiss the 26-year-old desegregation case that has cost more than $2 billion.

Student achievement is the last portion of the desegregation plan the court is monitoring. Whipple last year ended federal oversight in the areas of racial balance, facilities, budget and transportation.

A ruling is not expected until at least July. Whatever the decision, it is likely to be appealed.

Podgursky told Whipple that the loss of 20 white students to a French immersion charter school could have had a significant effect on the achievement gap because of the low percentage of white students in the district. Podgursky testified that fewer than 150 white juniors took standardized tests last year.

Experts for the district and the plaintiff schoolchildren disagreed Wednesday about whether the district had met terms of the court order.

A 1997 order required the district to reduce the test score gap by 13 percent in math and reading.

Whipple will have to decide whether the district has to close the 13 percent gap in every grade in both subjects, or just the majority of categories.

Podgursky testified that the district has closed the gap on state tests by more than 13 percent in nine of 12 categories. Students take Missouri Assessment Program (MAP) tests in four subjects in six grades.

But two experts for the plaintiff schoolchildren testified that improvement in nine of 12 categories is just 75 percent. They also noted that, at the high school level, the district failed to meet the 13 percent threshold in two of four areas.

Andrew Porter, a University of Wisconsin-Madison faculty member, and John Poggio, a Kansas University professor, said the district needs to exceed the 13 percent threshold in every grade for three to five years to merit regaining local control.