A thing that I've never understand is what are the marks in USA (or UK, I think that are similar). I know that exist letters, but i don't understand how they work. "A" is the best mark? Exist marks as "AA" or "BB"? Or i confuse school marks with financial ratings?
Explain me, please. Here in Italy, the lowest mark is 1 and the best is 10.

Well im from London, but I'm not sure it's the same all around england. but heres my school's...

A*, A, B, C, D, E, F, U

I think U is something like you can not be marked because it's so bad or something. B is bad to me. some people may think B is good, but Ireckon it's a bad grade.. The inbetweeny. You know? lol

I think* they are in order from highest to lowest... there are also effort grades which mean how much effort you put into your work and stuff.. 1 being the highest and 5 being the lowest.

We also have SATS grade which are supposedly something like the national curriculam level or something. And average for my year (year 9) is level 6-8.

Anyways I got B and above this year... It was pretty bad results considering what Iachieved last year. oh well, therse always next year.

We have the same in our school, A* being the best and U being the worst. Only a C or above counts as a pass on any of our tests. We also use an X grade for work that wasn't handed in or was late and Z for when someone was absent. U stands for ungraded as the work is deemed of a too low standard to get a grade.

We also get effort grades from 1 to 5, with 1 being the best and 5 the worst.

The letter grades are normally only given for GCSE and A Level students (Years 10 to 13). The SATs numbers are given from Year 1 to Year 9.

I think it's similar in most of America, at least I have it like this:

Grades:
A = Exceptional (highest)
B+ = Really good
B = Above average
C+ = A little above average
C = Average
D+ = Below average
D = Not good
F = Fail (lowest actual grade)

Other:
I - Incomplete (no grade, but doesn't count against you)
0 (zero) - No grade (factored in instead of a score -usually if you've cheated)

Some places include A+, some don't have +'s, and some include -'s which are like the +'s but a little lower than the letter. Most places also map the letters to a 0-100% scale. Mine is

94-100 = A
90-93 = B+
84-89 = B
80-83 = C+
74-79 = C
70-73 = D+
64-69 = D
<64 = F

but I hear most places are by 10's (90-100 = A, 80-89 = B, 70-79 = C, etc).