I'd say in general :
8 and 9 = Excellent
7 = Great
6 = Good
5 = Not bad
4 = At least you passed
1, 2, and 3 = Try again
But it really does depend on the person in question.
If my daughter gets a 4 or 5 I'd take it but I'd think she really hasn't put enough effort in. If my son gets a 4 or 5 though I'd be delighted.