Christel House's ISTEP test scores fell sharply this year, helping to contribute to its decline. It also was run through the grading formula accounting for all the school's grade levels.
Bennett's staff excluded the school's 9th and 10th grades from the calculations last year, which helped bump its grade from a "C'' to an "A''. A Ritz spokesman could not immediately say if the change in school configuration contributed to the sharp drop.
A Christel House spokesman did not immediately respond to a request for comment.
The State Board of Education approved the grades for all schools throughout the state at its meeting Friday morning. The grades have become increasingly important in recent years, being used to determine teacher pay, school funding and the potential for state takeover.
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 grading formula, which will also be used to calculate grades for the 2013-2014 school year. Members of the state board are crafting a new "A-F" grading formula.