8:40 p.m.
Arlene C. Ackerman's predecessor had some harsh words for her buyout.
Former CEO Paul Vallas, who left Philadelphia in 2007, said that "in this climate of fiscal distress with huge layoffs of teachers and administrators, to offer anyone $900,000 not to work is unconscionable. I think the people who agreed to this deal ought to have their heads examined.”
Of the private donations, Vallas said, “That’s about as outrageous as it gets. If you are going to raise $400,000 in private money, give it to a school, for crying out loud.”
Vallas got a buyout of $180,000 when he left the district in 2007. He went on to be schools chief in New Orleans, leaving that district this year.  He's now a consultant, doing work in Haiti on rebuilding schools there.

3:50 p.m.

By late June or early July of this year, a decision had already been made that Arlene Ackerman would move on, Mayor Michael Nutter said at an afternoon news conference.  He said he became involved to limit the amount of public money spent to buy Ackerman out.  Her contract entitled her to more than $1.5 million; she ultimately walked away with $905,000.
The district has had to cut $629 million from its 2011-12 budget already.  It must cut $35 million more.
Nutter declined to talk about what specifically Ackerman did wrong in his eyes. 
But he did say that "it was a pretty tough year given the magnitude of the budgetary challenges that we faced.  It’s just been a tough year." Ackerman angered Nutter in June when she blindsided him with her plan to save full-day kindergarten.
Nutter said he has long believed the mayor should have more say over what goes on in the district.  As for a possible change in the governance of the district, which is now run by a School Reform Commission, he said he doesn't believe there's enough support in the Pennsylvania General Assembly for that to happen now. 
The mayor repeated several times that he thinks the focus should be on opening schools on Sept. 6.  He said an appropriate amount of time should be taken to search for the next superintendent, but also said that time should be taken to determine what's needed in a schools chief. 
Answering questions about Acting Superintendent Leroy Nunery and whether he should have been appointed to his ex-boss's job, Nutter was clear.
"A transition is taking place," Nutter said. "We all need to move on."

2:10 p.m.

Acting Superintendent Leroy D. Nunery II said his immediate focus is very short term - on hiring teachers, preparing buildings and organizing buses to open schools successfully on Sept. 6.
"This has been a difficult time. … My goal is to do as much outreach to all our respective communities – and I do mean all,” Nunery said. 
“We need resources and we need friends - two key words,” Nunery said.
Nunery said he wants the superintendent's job long-term.

1:20 p.m.

On Thursday, Arlene Ackerman publicly challenged her bosses to release her in an emotional speech at the annual principals' convocation. (A district spokeswoman said at the time that it was not a farewell speech, but it was the last speech Ackerman gave.)
Of course, this morning Ackerman, the SRC and the mayor announced she was leaving.  The district has posted video of the speech on its website.  Watch that here.

12:45 p.m.

Philly.com's Daniel Victor looks at how the Ackerman story unfolded, and how people are reacting.  Check that out here.

12:05 p.m.

Arlene Ackerman's attorney characterizes the negotiations over her departure as "amicable" and confirmed that the superintendent gave up money for the final year of her contract to go straight to the district's Promise Academies, or overhauled schools.  They were her signature initiative.
The move was "the best thing for everyone," said Robert Nix.  "She's just giving back that last year and saying, 'earmark it for the Promise Academies.'"
"She essentially gets everything coming to her under her contract," said Nix, the attorney. 

11:30 a.m.

Arlene Ackerman's departure has been confirmed by the Philadelphia School District.  She will be paid $905,000 to walk away - $405,000 of that coming from anonymous private donations.
Here's the district press release from Ackerman, SRC Chairman Robert L. Archie Jr. and Mayor Michael Nutter:
“Today the School Reform Commission and Superintendent Arlene Ackerman have agreed that Dr. Ackerman will step down as Superintendent and CEO of the nation’s eighth-largest school district effective immediately,” stated School Reform Commission Chairperson Robert Archie.  “We have collectively made great strides, but we have much more work ahead.  The School Reform Commission and Dr. Ackerman are in agreement that the work begun by her requires us to focus our mission and resources on building a system of great schools for all children.
“All of us wish to acknowledge the substantial debt we owe Dr. Ackerman for her hard work and dedicated service to the District.  In 2008, when she was recruited to leave her tenured professorship and come to Philadelphia, less than 50 percent of the District’s students were at or above statewide standards for reading and math proficiency.  Dr. Ackerman immediately set out a comprehensive plan to target reforms that would close the achievement gap while raising the District’s performance across the board.  The aggressiveness of Dr. Ackerman’s five-year strategic plan, Imagine 2014, was outweighed solely by her personal commitment to demonstrating that given the right systemic reforms, all of our children can achieve.
“We see tangible evidence of the progress the District has made toward that goal in just three short years under Dr. Ackerman’s leadership.  Dr. Ackerman and her team earned praise from President Obama and Education Secretary Arne Duncan for an intervention approach aimed at turning around the District’s struggling schools under the Empowerment, Renaissance and Promise Academy initiatives.  Dr. Ackerman did not shy away from taking on the tough issues that had been neglected for decades such as rightsizing the District through a five-year master facilities plan aimed at better utilizing our resources and implementing new accountability measures for staff.  And Dr. Ackerman demonstrated real results:  three years of gains in test scores; a 29% decline in violent incidents; 7% gains in the six-year graduation rates; and lastly, Parent University where more than 40,000 parents took courses throughout the past three years.
“Throughout her more than 40 years in education, Dr. Ackerman has always put the needs of children above her own.  This decision, as difficult as it was for Dr. Ackerman, is consistent with her history, as well as recognition that for the District to best move forward, it must do so with new leadership.  We are all grateful for Dr. Ackerman’s service and wish her the best in her future endeavors.  Dr. Ackerman’s legacy will be long-lived, and we understand the passionate support she has in the community is a direct result of her commitment to serving the community.  That commitment will be honored.
“Although earlier this year Dr. Ackerman’s contract was extended another year through June 30, 2014, Dr. Ackerman and the Commission have agreed that any money that would have been owed to her under that one-year extension would be retained by the School District to be earmarked for the nine Promise Academies and utilized for their benefit.  According to Dr. Ackerman, ‘that is the best way to finalize the separation agreement because it still keeps the focus and emphasis on the children, as it should be.’
“Thus, by agreeing to this separation agreement, Dr. Ackerman and the School Reform Commission will help provide the District with opportunities to continue the Promise Academy initiative and other key Imagine 2014 initiatives.
“Effective immediately, the Commission has named Dr. Leroy Nunery as Acting Superintendent.  Dr. Nunery previously served as Deputy Superintendent/Deputy Chief Executive for the School District of Philadelphia and brings with him a wealth of experience.  The Commission will also launch a search to recruit a permanent Superintendent as expeditiously as possible.  As always, the Commission will continue to oversee the workings of the District, and we expect a smooth transition as well as an orderly opening of schools in September,” stated SRC Chairperson Archie.
“On behalf of the City of Philadelphia, I thank Dr. Ackerman for her service, her deep commitment to the city’s students and her educational expertise,” said Mayor Michael A. Nutter. “She took on many of the deep-seated, systemic issues that have been facing our schools for decades, such as low-performing schools long neglected, the right-sizing of the District’s aged facilities and new accountability measures for staff. During her tenure, test scores continued their upward trend, graduation rates improved and parents of school children became more involved with their schools. I plan to support many of the components of the Imagine 2014 plan, including turning around our lowest performing schools through the creation of Promise Academies and Renaissance Schools.”
Secretary of Education Tomalis said, “I thank Dr. Ackerman for her years of service in Philadelphia.  I look forward to working with Mayor Nutter and the School Reform Commission to improve opportunities for all Philadelphia’s children in the years ahead.”
Dr. Ackerman stated, “I am truly grateful for having had the opportunity and honor to serve the children and parents of Philadelphia.”
Arlene Ackerman is out as superintendent of the Philadelphia School District.  An announcement will be made later today, multiple sources say.
Asked when an announcement about the superintendent's departure would be forthcoming, a district spokeswoman said to expect something around 11:30 a.m.
Ackerman's departure has been rumored for months but as my colleagues and I wrote in Sunday's paper, it became clear last week that the end of Ackerman's superintendency was imminent. 
The money to buy out Ackerman's contract, which runs through 2014, will come from both the district and private sources, as The Inquirer previously reported. Sources say the district will pay about $500,000 and some amount - exactly how much isn't yet clear - will come from the private sources.
Leroy Nunery, Ackerman's deputy, will be the interim superintendent.  He was a finalist for the top job when Ackerman was hired.  A national search will be conducted for a permanent replacement.
Ackerman arrived in Philadelphia in June 2008 after stints as schools chief in San Francisco and Washington D.C.  She also worked as a professor at Columbia University. 
This is a developing story.  Please check back here for more details.  Follow me on Twitter, where I usually post news first.
--Kristen Graham, Susan Snyder and Jeff Gammage