@deathmailrock Huh can't blame you if you put it that way considering there is no dedicated chapter explaining how rich the school is, but I do know there has been hints in various occasions where most students are rich. Komi's dad got a black card, otori's mansion, kiyoko's politican dad, etc. Still, I think it's good for the series that doesn't really rely on school background and instead focused more on its characters.
The manga's detail is often subtle anyway, I wonder how many details missed by some people.