I forgot a piece of the story. When Emily saw something her brother had written, she noticed that he had put his age as 13, which was older than I expected.
It turns out he is actually 11 (or 12?). In Korea, they count ages differently. Emily said she's 15 in Korea but 13 everywhere else.
It might be easier to remember that they're in 6th and 8th grade, but the problem is that the grades in Russia are different from in the U.S. Kids are generally older when they enter elementary school.
I think someone should invent a calculator to translate ages between different cultures...