The author is a professor of education policy, and was given a contract to study private schools in India. He wasn't looking forward to studying what he thought would be expensive schools for the elite. However, while walking the back streets of an Indian city, he saw a cardboard sign advertising "St. Mary's School" with an arrow. He followed it and discovered a whole world of small homegrown schools for the poorest kids which were started by local people fed up with the poor quality of public schools. Apparently about a quarter of all Indian children go to these schools, while the government doesn't even acknowledge their existence. He later discovered the same phenomenon in poor countries around the world.