There is just one set of national norms for the SAT and they are based on everyone who takes the test, so mostly 11th graders. His scores and percentiles will reflect how he did in comparison to the most recent norming group, which will be as compared to high schoolers. Some of the talent searches also have percentiles as compared to other kids in the same grade, but I've never seen percentiles for age, which would be interesting to see especially for those kids who are not of the typical age for grade.
