This seemed relevant to your question:
http://www.davidsongifted.org/db/Articles_id_10405.aspx Any time your child has earned a score of 19 (the highest possible subtest score on the WISC-IV and SB5) on any individual subtest, OR any time your child has been administered all items on a subtest and the discontinue rule has not been reached, that subtest score and the overall composite score to which it contributes will underestimate your child�s true ability level, which is higher than the test is designed to measure. Ask your psychological examiner to consider including a statement in the report that test results may underestimate your child�s true ability level because of low subtest ceilings.
