ERIC Online Library
The Institute of Education Sciences of the U.S. Department of Education sponsors the ERIC online library (ERIC stands for Education Resources Information Center). In 2019 ERIC served 12 million users from 238 countries. ERIC's users accessed nearly 48,000 new records last year, many of them full text. Coverage and indexing goes back to 1966.
There is a free, government-sponsored version of ERIC, (the link in the first paragraph takes you there), but the librarians at Hekman recommend that you use either ProQuest or EBSCO to search, since the user interfaces are easier to use and have many special features. Types of documents indexed include journal articles, books, dissertations, reports, conference proceedings, meetings, government documents and audio visual media.