Middle-class schools educate the most students, but have surprisingly low achievement results, according to Third Way, a think-tank advocating moderate policy ideas.
The anonymous donors who pledged to support the deal withdrew in the face of suspicion over the deal.
School leader groups note that private-sector executives earn far more.
A school administrator caught up in the Atlanta cheating investigation was asked to resign after only one day in a new job.
Paul Vallas argues that his successor, Arlene Ackerman, took over a smoothly-running district when she started in 2008.
John Covington, who served in the 17,400-student district for two years, will oversee a system of underperforming schools throughout the state.
John Covington, the schools leader in Kansas City, said Wednesday he planned to leave the district in 30 days; James Williams, the superintendent in Buffalo, has also made plans to leave.
John A. Murphy, veteran superintendent and education leader, dies at 76.
In an interview, Ackerman said that she was blocked in her efforts by adults who want to keep the status quo.
The additional instructional time is proposed to begin in the 2012-13 school year.