Why can't you get an E on a test in the United States? So, in testing in the USA, an A is the best score you can get. Then comes B, which most students desire, and then comes a C, where you're on the verge of shattering your gradebook by getting a bad grade. Then there's D (even worse), and an F, where you will surely be very ashamed of yourself. Then, there's this alphabetical pattern, A, B, C, D, and then F. But where's E? Why isn't there an E in it?
In an answer given, I want a historical explanation of this question that tells how these letter grades popped up, and why E dropped out (or was never included) in the USA.
Thanks in advance!
I haven't located a super reliable source, but from Slate:

The earliest record of a letter-grade system comes from Mount Holyoke College in Massachusetts in 1897. [...] The lowest grade at Mount Holyoke was an E, which represented failure. [...] One year later, administrators changed the failing grade to F and tweaked the other letters. The new scale offered better symmetry, since each grade represented five points, with scores below 75 resulting in failure. [...] Over the next two decades, variations on the letter-grade system spread across the country and into primary and secondary schools. It’s hard to put a date on the end of the E, but it was gone from most colleges by 1930. Apparently, some professors worried that students would think the grade stood for “excellent,” since F stood for “failure.”

Basically, four grades (and plus/minuses) and a fail option seemed to work out well from the instructors' perspective, and F was picked up for &quot;fail.&quot;
Possibly the concern over &quot;E&quot; was affected by the ESNU system (according to an uncited paragraph on Wikipedia):

At one time (until roughly the mid-20th century), the most popular grading system in the United States used four letters, which ranked in descending order:

E (Excellent)

S (Satisfactory)

N (needs improvement; &quot;NI&quot; was also used interchangeably)

U (unsatisfactory)