INDIANAPOLIS — The Indianapolis charter school at the center of Indiana's grade-changing scandal has dropped from an "A'' to an "F'' in newly released school grades.The Christel House Academy benefited last year from grading changes made by former schools Superintendent Tony Bennett. But grades released for the 2012-2013 school year showed a precipitous drop for the school founded by top GOP donor Christel DeHaan.The grades are used to determine a range of important funding issues. The State Board of Education approved the grades at its meeting Friday.Bennett resigned as Florida schools chief in August after The Associated Press published emails showing he altered Indiana's school grading formula to benefit Christel House.The new grades were calculated using the Bennett model, but education leaders are developing a new formula.Bennett recently took a job with ACT.Before becoming Indiana's state schools superintendent, Bennett was the superintendent for Greater Clark Schools and served as a teacher and administrator in Southern Indiana.