children are self-taught their native tongue- they do not attend classes on their own language, but the languages of others. Conversing in languages is how self-taught learning is accomplished. Had the article indicated that he learned this plethora of languages by book I would have agreed with you, but, as it is I submit my counter-point.
Monitor: Airstrikes hit Islamic State stronghold in Syria, killing at least 13 (Reuters)
from the article: Teen polyglot speaks 20 foreign languages, first among them: Hebrew