From what we were told, there are age and grade norms available and I believe that the age norms are only broken into 3 or 4 groupings at most. For instance, I believe that kids from age 7yrs0mo-7yrs2.9mos would be in the 7 yr norming group. Ages 7yrs3mos-7yrs5.9mos would be in with the 7yr3mos norms, 7yrs6mos-7yrs8.9mos would be in with 7yrs6mos, and kids from 7yrs9mos up to just before they turn 8 would be in the oldest 7yr norms group.
Depending on your school, they may look at age norms, grade norms, or both. The 10 yr old 3rd graders in dd#2's class were certainly aided in terms of the grade norms last year by being older than typical.
