How did the United States improve education so dramatically between 1900 and 1950?

The United States went from ranking towards the bottom of the list of countries on metrics such as literacy rates, graduating drop out rates, and higher education degrees granted per 100,000 people to the top of that list between 1900 and 1950. What were the causes of this recovery and what can be learned by similar countries (specifically modern day Brazil) that rank near the bottom of these metrics?