"Your grades are above average" --Lose the "the," over would not work. "The interest rate of that bank is above 10 percent" "The interest rate of that bank is over 10 percent" --Add "The", either "above" or "over" works. Please don't ask me why, that's just what sounds right to me as a native speaker.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.