Primary collectors and distributors of statistics about education will be the U.S. Census, National Center for Educational Statistics, and states and districts. Start with articles about your research question for data source ideas. Also just browse these data collections to start seeing how others operationalize your concepts. Come see me for help locating statistics and data and refer to the data guide.
Intergovernmental agencies (IGOs) interested in development issues who would be collecting statistics as part of their work are often a good place to start your search for international statistics or data, or to start locating country profiles for case studies. Some sources will be the World Bank and the United Nations. Other sources will be NGOs, aid organizations, and researchers.