To find data you have to think about who collects the numbers. In the United States the government collects a lot of data and they share it for free.
You can go to the Education Research page on Statistics and Data for a list of websites where you can access statistics.
Below you can also find links to data from the U.S. Department of Education as well as from UNESCO and the EU.
The Department of Education collects a wide variety of data. Below are some of their most popular resources.
UNESCO, the European Commission and other organizations, both governmental and non-governmental, also collect data on education.