library school, educational institution providing professional training for librarians (see also library). Librarians were trained by apprenticeship until the late 19th cent. The first school for training librarians was established by Melvil Dewey in 1887. The success of this institution, combined with a shortage of librarians in a period of growth and expansion, led to a proliferation of such schools, many of which were inadequate. With the formation of the Association of American Library Schools in 1915, standards of accreditation were established and maintained. A number of university schools of library service were established in the 1920s, many of them funded by the Carnegie Corporation of New York.

In 1999, 56 U.S. and Canadian institutions offering training in librarianship were accredited by the American Library Association. These schools require a minimum of five years' study beyond the secondary level: The four years of undergraduate study constitute a general education in the humanities and natural and social sciences; the fifth year is in professional study at the graduate level and leads to a master's degree. The first school to confer the doctoral degree in library science was the Univ. of Chicago. Some of the schools are part of a university (as at the Univ. of Illinois); others are at independent undergraduate institutions (e.g., Pratt Institute). As libraries adopted the use of computer databases and on-line catalogs, the schools added a broader range of courses in information science and technology in order to acquaint future librarians with a variety of media.

The first library school outside the United States and Canada was founded at the Univ. of London in 1917. In many underdeveloped countries, university library schools have been established by grants from UNESCO and other sources, employing at the outset European- or American-trained staff. This staff is replaced as soon as possible with local personnel. Although the number of non-American library schools has steadily increased, many foreign librarians are still trained in the United States.