Updated

Melinda Gates, one of the most influential women in American education, said this week she gives the U.S. public school system a C-plus. But the co-chairwoman of the Bill & Melinda Gates Foundation adds there are spots of improvement that give her optimism for the future.

Gates bases her assessment on international comparisons of student achievement and on the fact that only a fraction of American high school students are ready for college when they complete their studies.

She says the pockets of improvement are growing larger and they're showing up across the nation, in places like New Orleans and in Florida, New York and Colorado.

For a decade, the Gates Foundation has studied education, influenced public policy and spent billions of dollars supporting education reform and demanding better results.