So practically speaking, what do these results tell us? I know that tests that give age/grade equivalents are saying how a child of a certain age/grade would have performed on that test, but how much can I derive about the target educational level for my child from the results?

DS5 scored 142 (Gr. Eq. 5.0) for broad reading (like some other posts on here, this score looked low compared to his subscores of 153, 145, 142, 155). and his brief reading was 153 (Grade 5.1). The report says his overall reading skills are on par with a year 5 student, while his comprehension is at year 4. The recommendation in the report is that his instructional level is likely year 4-6. Does WJ-iii ach for reading give fairly reliable estimates of reading levels?