Florida's education commissioner has resigned 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.

Tony Bennett announced his resignation Thursday morning in the wake of the scandal surrounding Christel House Academy, citing if he stayed on as commissioner it would "be a distraction to the children of Florida."

Bennett denied any wrongdoing. He said he has recommended that Pam Stewart, the state's current chancellor of public schools, serve as interim commissioner. The state Board of Education will decide whether to approve the recommendation.

"The resignation of Florida's latest commissioner of education is another symptom of the mistrust parents, teachers and the public have in the state's incoherent and unsound school reform and accountability policies. These policies have no value advancing education in this state and have lost the public's trust. These so-called reforms have tripped up another commissioner of education," said Florida Education Association President Andy Ford in a released statement. "As long as it is a political appointment, the office of the education commissioner will be a revolving door, and our students, schools and communities will continue to experience the whiplash of these policies. It's past time that we include teachers, parents and administrators in developing solutions, not just listen to the 'reformers' who have an approach that has been a disaster for public education in Florida."

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

Bennett lost his re-election bid last November in Indiana. He was hired by Florida as its education commissioner, a non-elected post, in December.

Indiana uses the 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. A low grade also can detract from a neighborhood and drive homebuyers elsewhere.

After Bennett learned about a likely low grade for Christel House, he fired off a Sept. 12 email 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, who was reworking Florida's grading system as the state's education commissioner, denied that DeHaan's Christel House Academy school received special treatment. He said 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.

Bennett downplayed the emails on Tuesday, repeating his assertion that he took action because he was concerned there was a flaw in the formula.

"It is absurd that anyone would believe that I would change the grade of a school based on a political donor or trying to hide schools from accountability," Bennett said. "That's fictitious at best, and it's totally unfounded."

He acknowledged that the problem was identified and fixed prior to the release of school grades but maintained the change affected as many as 13 schools.

"We did nothing wrong. We did nothing covert. We did nothing secretive," Bennett said.

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 earlier 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 by a 4-3 vote amid much debate and criticism that the move would "mask" the true performance of schools. Bennett's plan was even opposed by the education foundation set up by former President George W. Bush. 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.