A grade of A translates to a score of 90 percent or above; B translates to a score between 89-80; C between 79-70; D between 69-60; and a grade of F below 59. The grade scale helps standardize the performance of students.
With the letter A being the highest letter-grade and the letter F being the lowest letter-grade, this system allows for easy transition of numerical data to certain categories that help convey a student's performance.
The United States uses two main letter-grade systems, depending on the state: A-F going by ten points each, or a more strict and narrow system. This more narrow system designates a letter-grade of A to be 93 percent or above, B to be 92-86 percent, C to be 85-77, D to be 76-70, and F to be 69 or below.
A grade of A generally represents "high performing;" a grade of B may represent "above the average;" a grade of C might represent "average performing;" a grade of D can represent "below the standard" or "under-performing;" and a grade of F represents "failing" or "failed." Whatever the case may be, letter grades are used to differentiate students without the strict bounds tied to numbers.