There are several sources of free education data on the web. Both UNESCO and the World Bank have extensive collections of data available in easily downloadable format. Both sets of data include numerous tables, which have a large variety of data at a national level with time series. Both UNESCO and the World Bank also have tables devoted to the Millennium Development Goals -- the World Bank provides data at the country level while UNESCO provides aggregated regional data. UNICEF provides data on education as well, but it is not easily captured as a data file.
UNESCO -- the main UNESCO site provides a list of reports which can be downloaded as .pdf files, these are available at http://www.uis.unesco.org/Pages/default.aspx. Data ind downloadable spreadsheet format is available at http://data.uis.unesco.org.
World Bank -- The World Bank data uses much material from UNESCO and incorporates it with data from other sources. The World Bank provides time series data in the World Development Indicators and a dedicated education database both available at http://databank.worldbank.org/data/databases.aspx
UNICEF-- The UNICEF page provides a set of "At a Glance" data on population, nutrition, health, education, etc. as it affects children. This data is available only country by country and is not easily converted into a file. The UNICEF data is available at http://www.unicef.org/statistics/ .
United Nations -- Data on the educational indicators related to the Millennium Development Goals is available at http://unstats.un.org/unsd/mi/mi_goals.asp .