I would strongly echo polarbear. If you clearly define the problem as "reading concerns", it's not clear to me that retention would solve it - but it might create many more new problems. If there's a learning issue, more of the same won't help. If instead there's a temporary developmental lag, repeating won't help.
My totally biased, not-there, don't have all the info, two-cents worth is to deal directly with the problem area, reading, and tutor it directly (at school, home or external, whatever is most feasible).
I am a bit confused, though, trying to reconcile those extremely high reading-skills achievement scores with reading problems? Not sure what I am missing in terms of where she is having difficulty. If she can demonstrate specific skills at that kind of level, yet struggles to read in practice, that suggests you want to try and figure out what is different in the two scenarios. Vision, maybe, as a quasi-random thought? I don't know what the WJ tests look like, but I do know there's a big difference, if you have vision issues, between reading busy text vs reading single words on flashcards (with our reading remediation program, my DD almost never makes mistakes on the latter). Can you talk to tester, teachers, and from your own experience, and figure out what, exactly, is different from the tasks she performed on the WJ and the regular reading where you see struggle?
