I'm with drawntoblack on grades. You can't use school grades here.
5 is average and forgettable, 6 and up has some quality, below 5 it is terrible. 10 should be given just for genre defining albums.
In school you need to know 50 or 55% of the stuff just to get positive grade.
If we rated it based on school percents, we should use 5-10 (or 50% - 100%)
As this one has good productions, good instrumental and vocal work, good songs, some originality (although not that much) it should get somewhere between 7-8 IMO. Nothing spectacular, but above average.