, abbreviated , is Japan's oldest labor union of teachers and school staff. Established in 1947, it was the largest teachers union until a split in the late 1980s. The union is known for its critical stance against the ruling conservative Liberal Democratic Party (LDP) on such issues as Kimigayo (the national anthem), the Flag of Japan, and the screening of history textbooks during the LDP's near continuous one-party rule since 1955. Today Nikkyà Âso is affiliated to the trade union confederation Rengo. It had 290,857 members as of December 2009.
Nikkyà Âso was founded in June 1947, with assistance from the Japan Communist Party (JCP), as a national federation of local prefectural teachers unions, although in practice each of these unions had considerable autonomy and its own strengths and political orientation. At the time of its founding, Nikkyà Âso represented almost every single school teacher, university professor, and school staff member in Japan. Initially under the influence of the JCP, in 1950 Nikkyà Âso joined the nationwide Sà Âhyà  labor confederation and thereafter became more closely affiliated with the Japan Socialist Party (JSP).
From the earliest days of its foundation, Nikkyà Âso took an extremely militant line against a series of conservative governments in Japan, leading to considerable antagonism between the union and the Ministry of Education. Major points of contention included government requirements that teachers sing the national anthem and salute the Japanese flag in class, training requirements for new teachers, government efforts to recentralize education, efforts to protect school autonomy, government curriculum mandates, and textbook censorship.
From the perspective of the conservative government and right-wing groups in Japan, Nikkyà Âso was viewed as akin to public enemy number one, as it was seen to be indoctrinating Japan's youth and college students into left-wing, pro-union, and even communistic modes of thought. The decade of the 1950s saw successive conservative governments attempt to break the power of Nikkyà Âso by introducing a "teacher efficiency ratings system," which the government could then use as an excuse to fire the most militant teachers, and which Nikkyà Âso fought tooth and nail to prevent. In his book The Enigma of Japanese Power, Karel van Wolferen describes the clashes between conservative forces and Nikkyà Âso during this period, including Ministers of Education who had previously served in the "Thought Police" of the 1930s using thugs to systematically attack union members, break up union meetings, and eliminate local elected boards of education. In 1961, police even uncovered a plot by right-wing groups to assassinate the leaders of Nikkyà Âso.
In the latter half of the 1950s, however, Prime Minister Nobusuke Kishi made smashing Nikkyà Âso one of his personal missions. In 1958, Kishi finally succeeded in installing the long-delayed teacher efficiency ratings system, allowing the Ministry of Education to fire teachers almost at will. In the aftermath of this epoch-making defeat, Nikkyà Âso went into decline and began gradually losing members.
In the late 1980s, long-running internal disagreements within Nikkyà Âso on political orientation and on Nikkyà Âso's relationships to other national labor organizations finally produced major internal schisms. The union thus became less effective than in previous years at a time when the national government and the Ministry of Education were moving aggressively ahead with a major educational reform. Nikkyà Âso had staunchly opposed many of the proposed reforms by the Ministry, but it failed to forestall changes in certification and teacher training that it had viewed as an existential threat to its own survival. The new Nikkyà Âso leadership that emerged after several years of internal discord seemed to take a more conciliatory approach to the Ministry and reform issues, but Nikkyà Âso membership continued to decline thereafter.