U.S. Department of Education: Datasets, data visualization tools, and applications created from open data. Datasets are gathered from various agencies.
ICPSR: Inter-university Consortium for Political and Social Research is a data archive for the social sciences, including education (teacher resources included)
State datasets:
Idaho Schools Data: Student achievement stats at state, district, and school levels; NCLB/AYP, and ISAT data.
State Education Data Profiles: Compare states on education data such as demographics, finances, enrollment, public libraries, and post-secondary education.
Statistics:
National Center for Education: The National Center for Education Statistics (NCES) is the primary statistical agency of the U.S. Department of Education. It is one of thirteen principal federal statistical agencies1 whose activities are predominantly focused on the collection, compilation, processing, or analysis of information for statistical purposes.
National Education Association | Reference Center: NEA annual reports on American school teachers, school readiness, school rankings, achievement gap, quality learning conditions, assessment, and funding.
U.S. Census: Education: Formal education by age, school enrollment, educational attainment, financial aspects, charter schools, computer usage, etc.