I have a distribution of discrete values (grades, from low to high) where I see that the certain groups have a higher frequency of observations in the higher ranges and less in the lower ranges than other groups. Eyeballing the histogram they are thus performing better.
I would like to see if these differences in the different groups are significant. e.g. is it true that group B has significantly less (more) low (high) grades compared to group A.
Is it best if I decompose the data between the different ranges (high/low)? Or are there other techniques that could be useful?