"Is there anyone you like in school?" => 학교에 (네가) 좋아하는 애가 있니? (plain) => 학교에 (네가) 좋아하는 애가 하나라도 있니? ("anyone at all you like") 학교에(in school) 좋아하는(that you like) 애가(boy, girl, someone) 있니(is there)? "anyone" in this case doesn't need to be translated to 누구. If a question is about existence of someone in a school with a multitude of students, "anyone" is already implied. If you want to emphasize whether there's even one ("anyone at all"), you can add 하나라도 (even one).