There are some firms that are very elitist in terms of their resume review requirements. You should note that for a place like Jane Street, "Harvard" helps, but it won't get you an interview. Someone who has done well at USAMO or IMO or has meaningful open-source contributions and goes to SUNY or a community college will generally have a better chance than a run-of-the-mill Harvard student. The median Harvard Math/CS student isn't getting an interview at Jane Street.