INDIANAPOLIS (AP) _ Indiana's A-F grading system designed to hold schools accountable faces an uncertain future as state leaders review it to ensure that marks awarded are fair and impartial.
 
  The Indiana Department of Education is reviewing all grades awarded under an A-F system implemented by former schools chief Tony Bennett. The review followed revelations that Bennett and his staff changed the formula to improve the score of a top Republican donor's charter school.
 
  Bennett resigned Thursday as Florida's education commissioner.
 
  An Indiana teachers union called Thursday for the grading system to be suspended. Many school superintendents say they don't want a system “connected to corruption and manipulation.''
 
  Superintendent Glenda Ritz has ordered a review of grades. Republican Gov. Mike Pence says he supports the system but that a review is in order.