Gale Virtual Reference Library includes, among many others, the following electronic education-related encyclopedias:
Search results in the Gale Virtual Reference Library will include all encyclopedias unless you click on a specific title and use the Quick Search box within the specific title page
Oxford Reference Online
With over two million entries, Oxford Reference Online is a superb cross-searchable resource to use when you are at the "looking for a clue" or "needing verification" stages of your research. Oxford Reference provides quality, up-to-date information from a series of well-respected books--and unlike Wikipedia you can cite Oxford Reference in a paper!
Historical Dictionary of American Education
Print Location: Ref LB15 .H57 1999
Dictionary of concepts, pedagogy, trends, legislation, people and places with historical significance to the development of education in the United States. Arranged alphabetically by topic, not chronologically. Includes bibliography. Useful for biography of educators, as well.