Eli5: In American schools, the letter grading scheme is: A,B,C,D and F. Why did it skip the letter E?

Question

I was wondering why the letter grading scheme is like this. Why did it skip the letter E?

In: Other

Answer 1

Funny, my elementary school used “E” to denote “Excellent” as part of the grades for conduct. So, you’d get your letter grades of A-F for subjects/classes but then your conduct in those classes was graded either N-not satisfactory, S-satisfactory or E-excellent.