The grading system and interpretation of letter grades used for students in public schools in grades 6-12 shall be as follows:(1) Grade “A” equals 90 percent through 100 percent, has a grade point average value of 4, and is defined as “outstanding progress.”

(2) Grade “B” equals 80 percent through 89 percent, has a grade point average value of 3, and is defined as “above average progress.”

(3) Grade “C” equals 70 percent through 79 percent, has a grade point average value of 2, and is defined as “average progress.”

(4) Grade “D” equals 60 percent through 69 percent, has a grade point average value of 1, and is defined as “lowest acceptable progress.”

(5) Grade “F” equals zero percent through 59 percent, has a grade point average value of zero, and is defined as “failure.”

(6) Grade “I” equals zero percent, has a grade point average value of zero, and is defined as “incomplete.”

For the purposes of class ranking, district school boards may exercise a weighted grading system pursuant to s. 1007.271.