Why do US school grades go A, B, C, D, and F. Why not "E"?

为什么美国学校的成绩有 A,B,C,D 和 F ，唯独没有 E ？

原文地址：https://www.quora.com/Why-do-US-school-grades-go-A-B-C-D-and-F-Why-not-E

Robert Frost:

The modern letter grade system began at Mount Holyoke College in Massachusetts in 1897. The system was picked up by other schools and within about 20 years had become the norm across America. During this same period, immigration and mandatory attendance laws were resulting in more crowded schools and a higher student-to-teacher ratio. The letter system caught on with teachers because its simplicity made their job simpler as they became responsible for grading more students. Also at this time, it became more of a standard to report grades to parents, so a scale that was easy for parents to understand was desirable.
现代成绩系统起源于 1897 年马赛诸塞州的 Mount Holyoke 学院。这套系统在随后的 20 年内传播至其他学校直至整个美国。在这段时期，移民和强制性出勤法规导致了学生的激增和学生-教师比例的增大。在面对大量的学生的情况下这套简单的评分系统使得教师的工作更加轻松，因此在教师群体中广受欢迎。同样也在这一时期，这也成为向学生父母汇报成绩的新标准，这样一套方便易懂的标准对于父母而言同样是令人满意的。

Mount Holyoke defined their original scale as follows:
Mount Holyoke 学院是这样定义成绩的：

A Excellent, equivalent to 95-100%
A 优秀，大致相当于 95-100%

B Good, equivalent to 85-94%
B 良好，大致相当于 85-94%

C Fair, equivalent to 76-84%
C 中等，大致相当于 76-84%

D Passed, equivalent to 75%
D 及格，大致相当于 75%

E Failed, less than 75%
E 不及格，低于 75%

E was quickly replaced with F, because "F for failed" was more intuitive than "E for... excellent or failed?"
E 很快就被 F 所取代，因为“F代表 failed”比 E“excellent（优秀）”更加合适。