Wiktionary
letter grade
n. (context education English) One of the letters ''A'', ''B'', ''C'', ''D'' or ''F'' assigned as an evaluation, with ''A'' the best passing grade, ''D'' the worst passing grade, and ''F'' a failing grade. Passing grades may also carry a plus or minus sign, with an A-minus (''A-'') better than B-plus (''B+'') and so on.
Usage examples of "letter grade".
The attached commentary sheets--every teacher did a short paragraph to supplement the letter grade--noted that the quality of the homework turned in had improved in the past few weeks .