Bluematter.

Deworming is the most cost-effective way to improve school attendance and performance in developing countries:

The simplest and least costly of these programs is deworming. Nearly 2 billion people around the world are affected by parasitic worm infections, with children disproportionately affected.

Harvard economist Michael Kremer has studied the impact of mass deworming in Kenya and India. Delivering deworming medication costs 50 cents per child per year in Kenya but yielded a 25 percent increase in school attendance; a similar program in India cost $4 per student per year and yielded a 20 percent attendance gain. "This is a simple, cost-effective and yet tragically not-done program. It's a scandal that [deworming] hasn't been addressed," Kremer says. There are spillover effects as well. "The most surprising thing about the study in Kenya was the widespread impact," Kremer says. The program drove down infection rates for several kilometers around the schools, he says, and there were significant improvements in attendance for untreated students, in the treatment schools as well as in nearby schools not in the program.