In schools, what is the range of alphabetical marking? is it from A to F or A to F-?

Question

what would be 18.5 out of 20? is it A or A?

Answer 1

the range is A to F. A, B, C, D, F.

18.5 out of 20, rounded, would probably be an A. either an A- or B+.  

Answer 2

also, when you write papers and stuff like that, the teacher could also give you an A+, but it has to be flawless.

Answer 3

According to my calculation it is a 90 which is a A. Hope this helps.

Answer 4

F is considered Failing, so an F- would be redundant.

I have heard of an "0" grade, on a percentile scale.