I do get a little confused on what it means that kids with aspergers have great reading skills but little comprehension.
I once tested a middle school student with autism who recognized words and read aloud like a high school student, but answered comprehension questions like a second grader. A big part of the issue with autistic students is that they might answer the first question or two correctly, but later questions are answered out of their own experience or imagination instead of the story.
In general, formal assessments for autistic students are of limited use. You might accidentally find out they can do something you didn't know they could do. But between the accommodations you have to make in order to just get through the test, and behaviors like perseverating during a timed portion, the results won't have much statistical meaning and won't tell you anything about what they can't do.
