MADISON, Wis. (AP) — Supporters of charter schools had a champion in Tony Bennett, the former Indiana schools chief who installed a school grading system that cut the time it took to sweep away a failing public school in favor of charters.

But Bennett's involvement in a grade-changing scandal is making them nervous.

Emails uncovered by The Associated Press showed Bennett's efforts to make sure one charter school he had highlighted scored an “A.” He's denied wrongdoing.

But some charter supporters say the fallout could shake the public's confidence in charters.

Frederick Hess, director of education policy at the conservative American Enterprise Institute and a Bennett admirer, said what's needed is a school grading structure that protects officials from public pressure and the appearance of impropriety.