Pittsburgh Public Schools Superintendent Mark Roosevelt abruptly removed Allderdice High School's new principal a month into the school year and brought back the school's retired principal on an interim basis.

Mr. Roosevelt yesterday declined to say why he replaced Kevin McGuire on Thursday. The school board had appointed Mr. McGuire to the helm of Allderdice, one of the district's flagship schools, as part of a shuffling of administrators in May.

Dr. Cassandra Richardson Kemp, who retired as Allderdice principal June 30, sent parents a letter over the weekend saying she has returned as acting principal during a national search for Mr. McGuire's replacement.

George Gensure, a member of the Pittsburgh Federation of Teachers' executive board, said district officials were unhappy with Mr. McGuire's handling of student and faculty scheduling problems related to a higher-than-anticipated enrollment.

"It seems to be the rule of thumb now with our new superintendent: Things don't languish anymore. If something needs to be modified or changed or whatever, they do it," Mr. Gensure said.

Mr. Gensure said Mr. Roosevelt likely acted quickly to prevent Allderdice, one of the district's best-performing high schools, from slipping. He added that the Squirrel Hill school has a vocal parent base.

The district said Allderdice's enrollment Thursday was 1,678, which is 74 students more than projected in February.

Ninety-seven students this school year have requested reassignment to Allderdice from high schools that repeatedly had missed federal performance requirements, but the district wasn't able to say whether last week's enrollment report included those students. The district must offer transfers from lagging schools under the No Child Left Behind Act.

Jody Buchheit Spolar, director of employee relations and organizational development, said the school district and Mr. McGuire decided it was in their "mutual best interests" for him to take another position. She said details of the new job should be ironed out this week.

Mrs. Spolar said the district was negotiating payment with the interim principal, Dr. Kemp, one of 22 administrators who retired June 30 under an incentive plan.