Changes in the executive suite are coming to some of the nation's largest school districts. In four of the five largest systems, the chief executives who began the 2010-11 school year will have departed by 2011.

In New York City, publishing executive Cathie Black is Mayor Michael Bloomberg's choice to replace Joel Klein as head of the nation's largest school system. Black's selection has prompted criticism because she has no background in the education field, but after she agreed to appoint Shael Polakow-Suransky as chief academic officer, the state's education commissioner agreed to grant her a waiver that will allow her to serve as schools chancellor.

In Chicago, the third-largest U.S. district, CEO Ron Huberman has resigned in anticipation of Mayor Richard Daley's retirement. Terry Mazany, president of the Chicago Community Trust, has agreed to serve as interim schools CEO until a new mayor is elected in 2011.

Ramon Cortines, the superintendent of the nation's second largest system, the Los Angeles Unified District, has announced that he will retire in Spring 2011.

In October, the Clark County (Nev.) district, the nation's fifth largest school system, appointed Colorado Education Commissioner Dwight Jones as its new superintendent.

Turnover is occurring at other urban districts, too. Michelle Rhee ended a three-year stint as chancellor of Washington, D.C., schools after the mayor who appointed her lost a reelection bid. In Atlanta, which has been saddled with a testing scandal, Superintendent Beverly Hall has announced she will leave the district after 11 years.