My son had a drop in WJ IV scores. It was fairly dramatic- the neuropsych was testing for ADHD. He said that my son was very distracted during certain portions of the test. Because of the age norms, my DS had to go further on the test this time to achieve such high scores. The reading and writing and even some of the math pushed his ability to remain focused and careful.

Even a year made a difference on achievement tests. We saw a similar result on his school standardized test. DS was able to explain what was going on in the room during the test, but the test itself did not garner much attention.