From Quora: My Answer to: "Will a college admission officer assume that a high school student who takes a foreign language that is spoken at home is a slacker and is not challenging himself?"

Not necessarily, but such a student had better get VERY good grades in the courses, since they’ve had an obvious “head start.” A native speaker of English can major in English in college, and our hypothetical home-foreign-language speaker would be able to major in his home language at the same school (assuming it were offered there, etc.).
​

I don’t think a college admissions committee would see such a student as a slacker, since he/she might want to learn the “proper” version of that language, which his/her family might not speak at home. At least, the student’s choice of foreign language wouldn’t be any more of a “slacker” move than a monolingual English-speaking student who decides to take Spanish (relatively easy) rather than Mandarin (relatively hard). In any case, that’s just one course, so if you take challenging courses in high school (physics, calculus, just about any AP course), they’re not likely to give a student a hard time about taking courses in his or her family’s native, non-English language.
I have no ego about this response- if someone who is/was actually a college admissions officer wants to contradict me, so be it- I’d love to hear from such a person to hear what s/he has to say.