The Milton and Rose D. Friedman Foundation provides a huge amount of information on vouchers as their major advocates. They also provide much backgound information on school choice, its research through online articles and links. Milton Friedman a Nobel Laureate economist and Rose Friedman, also an economist, are an unabashed supporters of “school choice to improve, through competition, the quality of K-12 education for all.” This is a good source of background and current information on vouchers and examples of their implementation.
