Cheap and easier access to free online prep courses would help. Also there's a lot that can be done by bringing kids into a community and giving them a group to belong to that encourages education. Freakonomics did a pretty good podcast about a project in Toronto that cut the dropout rate by ~15 percentage points. [0] The whole thing is worth a read but the basics are they provided support advocates, transportation, a scholarship if they kept with the program, tutoring, and group activities.

Really though there's probably always going to be some level of education outcome gap between rich and poor kids, having an easier and more stable home life is a substantial leg up.

[0] http://freakonomics.com/podcast/fix-broken-high-schooler-fou...