Her son, Anthony Antognoli, told the Associated Press that Ackerman died at about 5 a.m. of pancreatic cancer in Albuquerque, N.M., where she lived. He said she hadn't been ill long and "it was too short a battle."
She was 66 years old.
In a written statement, current Superintendent William Hite said "On behalf of The School District of Philadelphia, I would like to extend my deepest sympathies to the family of Dr. Arlene Ackerman and all who loved her."
"Dr. Ackerman devoted her life to children and public education, and in doing so, encouraged countless other individuals to commit their lives to teaching, learning and leading," Hite's statement continued. "For that, we are grateful. Our thoughts and prayers are with her family, friends and colleagues."
Mayor Michael Nutter praised her as "a truly committed educator who demonstrated a profound passion for students and in particular the most disadvantaged students in our city.
"Through her leadership, Philadelphia took on the difficult, long-neglected task of turning around low-performing schools," he said in a statement. "Today, thousands of Philadelphia students are getting a better education thanks to her vision and advocacy. Her educational legacy will live on for many years through the initiatives that she championed."
During her tenure, Ackerman clashed with the teachers union after trying to protect certain staff from layoffs.
"Arlene Ackerman was a dynamic personality whose passion for children is to be admired," Jerry Jordan, president of the Philadelphia Federation of Teachers, said in a statement. "While we may have disagreed about some educational issues, we always kept what's best for children as our focus.
"We will always remember her as a staunch advocate for Philadelphia's school children who believed that every student should have equal access to a quality education."
Ackerman was dismissed as superintendent of Philadelphia schools in August, 2011, shortly before classes were set to begin. The end of her tenure was the source of controversy after it was learned she was given $905,000 in school district money to walk away.
Ackerman is credited with continuing the district's rise in test scores as well as lowering class sizes in primary grades, creating a parent-outreach program and launching an initiative to transform chronically failing schools through staff overhauls or conversion to charter schools.
But critics called her "Queen Arlene," saying she was polarizing, autocratic and overpaid.
An educator for 43 years, Ackerman previously served as superintendent in San Francisco and Washington, D.C. She came to Philadelphia, the nation's eighth-largest district, in 2008.
According to an archived biography on the School District of Philadelphia's website, Ackerman received her doctorate in Administration, Planning and Social Policy from the Harvard Graduate School of Education, Urban Superintendents Program. She held a Master of Arts in Education from Harvard University, a Master of Arts in Educational Administration and Policy from Washington University, St. Louis, MO and a Bachelor of Arts in Elementary Education from Harris Stowe Teachers College.
Ackerman is survived by sons Anthony and Matthew Antognoli, as well as siblings and granddaughters. Funeral arrangements are not yet complete.
The Associated Press contributed to this report