The ITBS is one of those tests where the grade equivalencies given have to be taken with a grain of salt. A 4th grader who gets a score that says he is at 11th grade equivalency scored as well as the average 11th grader (a kid who is at the 50th percentile of 11th graders nationwide) would have were he given that same 4th grade test.
My oldest took the ITBS only in 3rd grade. What I found more meaningful than the grade equivalencies were the percentiles which told us how she stacked up with kids in her grade: 3rd. She was in the 99th percentile as compared to 3rd graders on every section of the test except math, which was still in the 90s, and the composite score was also 99th. FWIW, she wound up skipping a grade shortly thereafter and that seems to have been a good choice.
If your ds is also coming out in the 99th in many or all areas, which sounds like a good possibility, I'd certainly want to know what type of acceleration or other options he has available.
