Tenure, the practice of assuring professors (1) continuation in their positions (2) they have passed successfully through a probationary period and provided they are not later found seriously deficient (3) a carefully specified procedure, is an important protection of academic freedom. (4) academic freedom of untenured professors, and of students' is not formally protected, (5) of equal concern in academic (6) . Until the student movements of the 1960s, the United States lagged in (7) student academic (8) ; statements on student academic freedom (9) been issued by the AAUP and the American Civil Liberties Union (ACLU). The U. S. Supreme Court has given legal (10) to academic freedom claims as falling (11) , the First Amendment in decisions such (12) Sweezy v. New Hampshire (1957) and Perry v. Sinderman (1972). (13) such actions, challenges (14) academic freedom regularly occur and have become acute (15) critical stages in U.S. history. Following World War Ⅱ, (16) example, the credentials of academics suspected of Communist-party affiliation were often questioned, and teachers were dismissed as actual or (17) Communists. In the late 1980s some American colleges and universities tried to prevent speech offensive to minority groups. (18) endorsing efforts to discourage such speech, (19) both faculty and students, the courts ruled explicit speech codes designed to enforce "political correctness" unconstitutional as (20) the First Amendment, and the ACLU condemned the codes as undermining academic freedom. The codes were abandoned by the end of 1993.