Why isn't E a letter grade?

Question

There is A, B, C, D, and F but no E. Why?

Answer 1

when I was in school you had

E for excellent

S for satisfactory

U for unsatisfactory

OR in other schools

A for excellent

B above average

C for Average

D below average

F fail

My guess is so you don't get mixed up.

Now my kids school as

+

-

\__

what the heck is THAT all about?

Answer 2

Some schools do actually use the letter "E" instead of "F". My Junior High and High School did.

Answer 3

E stands for EXCELLENT

F stands for FAIL ;)  

Answer 4

there's basically a, b, c, d and fail, but fail just happens to start with F

Answer 5

you cant spell fail with an e at the beginning, now can you?