Your max values are the same as the min values for the next grade. If
someone has a score of 2 or 5, which grade would be awarded? Assuming
that it would be the higher grade, the following should do what you
want:

=VLOOKUP(A1,$H$2:$J$9,3,TRUE)

where I have assumed your table (with headings) occupies cells H1 to
J9, and that the raw score is in A1. You can enter the formula, say, in
B1 and copy down.

Hope this helps.

Pete