I actually think that is quite normal. Davidson has an article which notes how kids scoring the 99th percentile on grade level tests aren't at the same achievement level and that this is where an above level test can give you an idea of how far above level the kid is.
Scroll down a ways here:
http://www.davidsongifted.org/db/Articles_id_10150.aspx to see the following:
"VanTassel-Baska (1986) showed the appropriateness of using the SAT as an above-level test, and as a diagnostic tool. The following table was adapted from table presented in her article.
Table 1
Breakdown of SAT Score Ranges of Students Scoring in the 99th Percentile on In-Grade Achievement Tests SAT-M
Range % Students
Scoring SAT-V
Range % Students
Scoring
200-300 2% 200-300 6%
310-400 21% 310-400 39%
410-500 40% 410-500 40%
510-600 29% 510-600 13%
610-700 6% 610-700 2%
710-800 1% 710-800 1%
(Rounded) (Rounded) "
Basically, they took kids who scored in the 99th percentile on a grade level math or reading test, gave them the SAT as an above level test and had scores come out ranging from 200-800.
FWIW, we see something similar w/ our dd12. Pre-skip, she scored in the upper 90s on grade level math and reading achievement tests. Math was usually a bit lower than reading (97 vs. 99, for instance). Post skip, her math came out mid 90s and reading still 99th. On above level tests, in verbal areas (reading/english) she scores still in the 80s+ (97th on part of the ACT recently) as compared to high school kids, but more average as compared to high school kids (50s or so) on the math portions.
