Like Carrot said- it all depends on the person. There are a lot of people that would be extremely happy (and very rightly so) with a B6; there are others who would be disappointed. I always try to look at these things in terms of individual potential and doing your best. If there is someone who's potential in maths is 88 and they get 88, they have done fantastic and should be congratulated. On the flipside, if there is someone who has the potential to get 100 but gets 97 because they don't put in the effort- then that's a poor showing.
You shouldn't really compare yourself with others because everyone has different abilities in different areas.