They did the WJ achievement although I have not seen that report yet. She did say he scored at 2nd to 3rd grade.
I'm sure that they'll give you the full breakdown with the report you get, but the number you have right now might not be telling you the whole story. My dd13 took that WJ-III and WISC-IV when she was 7 and, while she scored around 5th grade overall on the WJ, she had wild variation within it. She really isn't a 2e kid. Some of it was due to lack of exposure, some of it due to perfectionism, and some of it represented real strengths and weaknesses. As I recall, she was at grade 18+ on writing and maybe another part related to language arts. She was barely at grade level on one part related to timed math facts or something like that. Honestly, I don't think that she was really functioning at a postgrad level anywhere at that age, but overall those are her strengths and weaknesses seven and a half years later. She's a superb reader and writer and pretty average in things related to speed. Math is strong, but not HG+ by any means (more MG).