Yup, I and those around me experienced very similar things.
1. I was also 9 when we arrived here, but we ended up in a rural area that did not have ESL classes, and for the longest time, we were the only Russian-speaking students in our school (long enough that I didn't feel the urge to communicate with them once they arrived, on a regular basis). My math also fell to an above-average level, but I never really cared for it beyond thinking it was nifty.
2. My brother (19 years my junior) experienced something very similar to your nephew, but we took it in stride and he adjusted very quickly.
3. My wife also came from Russia only 5 years ago, she experienced the same feelings as your wife did.
4. We also are experiencing a fourth experience: our oldest speaks Russian fluently for her age. In order for her not to experience shock when she went to kindergarten, we started speaking English with her for about half the day about six months before she started kindergarten (and really, we intentionally exposed her to English all along, but focused on Russian at first). Now that she's in kindergarten, she understands almost everything, and can communicate well enough that she doesn't need to attend ESL, although she still doesn't know all the words in English that she does in Russian.
By the way, where are you located?