My advisor's research on a practical and surprisingly cheap improvement to demand-side education results: give glasses to the kids who need them (presented on the Freakonomics blog). Glewwe and Park find that wearing glasses for an entire school year yielded 25-50% increases in test scores (reading and math) for kids in rural China. That's pretty remarkable, especially considering how cheap and simple this improvement was.
A surprising 30% of kids refused the glasses, though, likely because a lot of them think that glasses just aren't that cool and they're afraid of getting teased. I guess cool Chinese pop icons haven't delved into the hipster or thick framed glasses styles just yet.