TALLAHASSEE, Fla. (AP) — Florida's education commissioner resigned Thursday amid allegations that he changed the grade of a charter school run by a major Republican donor during his previous job as Indiana's school chief.

Commissioner Tony Bennett announced his resignation, effective immediately, at a news conference. He said that while he did nothing wrong he didn't want to be a distraction to ongoing efforts to overhaul Florida's education system.

The Florida State Board of Education will hold an emergency meeting Friday. Board members are expected to name Pam Stewart as an interim commissioner. Stewart, who is currently chancellor for the division of public schools, served as interim commissioner before Bennett was hired.

Emails published by The Associated Press this week show that Bennett and his Indiana staff scrambled last fall to ensure Republican donor's Christel DeHaan's school received an A, despite poor 10th-grade algebra scores that initially earned it a C.

Bennett called that interpretation "malicious and unfounded" and said he would call for Indiana's inspector general to look into the allegations because he is certain he will be cleared of wrongdoing.

He said it would be unfair to Gov. Rick Scott "to have to spend my time and the State Board (of Education's) time, as things continue to trickle out, defending myself." Bennett called the allegations "politically motivated." He said the decision to step down was his and that both Scott and former Gov. Jeb Bush, both Republicans, had urged him to remain on the job.

"The decision to resign is mine and mine only because I believe that when this discussion turns to an adult, we lose the discussion about making life better for children," Bennett said.

Bennett lost his re-election bid last November in Indiana. He was hired a month later by Florida as its education commissioner, a nonelected post that pays $275,000.

Scott, at an appearance in South Florida, said he had not fired Bennett or demanded his resignation and called it "his decision." He said he done a "good job" but refused to answer questions about the accusations against Bennett in Indiana.

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The GOP governor did put out a statement later in the day.

"He made a difficult decision today with the best interest of his family in mind, and he will no doubt continue to make a great contribution wherever he chooses to serve next," Scott said.

Bennett is the third education commissioner to leave office since Scott became governor in January 2011.

Bush, in a statement, praised Bennett for the work he had done in Indiana.

"Tony started every day with the focus of creating a system that would equip kids to achieve their God-given potential," he said.

Stewart would take the helm at a critical time. Bennett was poised to decide whether Florida should remain with a national consortium or develop its own set of tests for new common core standards that are scheduled to take effect. Florida's Republican legislative leaders want the state to develop its own assessments.

"It's the worst possible time for the resignation," said Kathleen Shanahan, a member of the state board. "We are at a tipping point in our ability to be effective for implementation of common core."

Bennett's decision to resign came even though he had gotten support from board members after the initial reports from Indiana came out.

"I regret that Commissioner Bennett feels he must resign, but I respect his decision," said John Padget, a state board member from Key West.

Indiana uses A-F grades to determine which schools get taken over by the state and whether students seeking state-funded vouchers to attend private school need to first spend a year in public school. They also help determine how much state funding schools receive.

After Bennett learned about a likely low grade for Christel House, he fired off an email last Sept. 12 to his chief of staff.

"This will be a HUGE problem for us," Bennett wrote. "They need to understand that anything less than an A for Christel House compromises all of our accountability work."

Bennett denied that DeHaan's Christel House Academy school received special treatment. He said earlier this week that discovering that the charter would receive a low grade raised broader concerns with grades for other "combined" schools — those that included multiple grade levels — across the state.

The revelations that Bennett and Indiana officials scrambled to change the grade of one school come amid a strong debate over Florida's grading system.

Bennett this month pushed the Florida board that oversees education policy to adopt a "safety net" provision that prevented the grades of more than 500 schools from dropping more than one grade this year.

That provision was adopted amid debate and criticism that the move would "mask" the true performance of schools. The grades released last week still showed a sharp drop in the number of A-rated schools and a jump in the number of F-rated ones.

Andy Ford, president of the Florida Education Association, said Bennett's resignation is "another symptom of the mistrust parents, teachers and the public have in the state's incoherent and unsound school reform and accountability policies."

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Associated Press reporter Kelli Kennedy in Delray Beach, Fla., contributed to this report.

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