My kids aren't in a language immersion program but we have had a number of friends who are and we attended intros to our local immersion programs when our children were entering kindergarten in hopes they might lottery in... so fwiw (which is probably not much lol!) what I've always been told is that the immersion student's English (reading/writing) achievement lags a bit behind non-immersion kids for the first few years of elementary, but generally catches up by 3rd - 4th grade. I'm sure the school psychologist is most likely familiar with testing children who are in the immersion program, so if she doesn't address it in her report you can always ask her about it.
I'm also guessing that if he really was given a grade equivalency # and if he was taking a true "spelling" test is that he was given the WIAT achievement battery in addition to the WISC. The WISC really doesn't take 2.5 hours (at least not in our experience), and I've also never seen a grade equivalent from an IQ test, they come with achievement tests. Like Cricket mentioned - it's really highly unusual for a psych to tell a child exactly what their score is or how they performed relative to other students on this type of testing - the info is usually given to the parent, and if a student asks they would be told something like "you did very well".
Best wishes,
polarbear
