But where I live (in San Francisco) speaking exactly 2 languages is usually a sign that you or your parents are immigrants.
India for instance -- A typical kid in many places here (especially southern part of the country) has 3 languages formally taught in school and consumed as popular media daily.
Having privilege in these regions usually translates to levels of literacy like having reading ability (in addition to just speaking for trade), reading literature, speaking fluency, broader vocabulary, "better" accent, etc. -- all of which, in thousand different ways, signal one's socio-economic status in every interaction.
For instance, immigrants will massively be bilingual in general. We could argue there are in a better financial and educational position than those who couldn't immigrate in the first place, but then relative to the country they live, they can be on bottom of the social ladder.
On the parrallel with studying other subjects, I think it rings true, the only difference would be that bilingualism can be "forced" upon children by circumstances or environment, where math or instruments usually come later and/or on a choice basis.