Answer by taking a quote from the following article:

Gyorgy Sandor Ligeti (; Hungarian: Ligeti Gyorgy Sandor, pronounced ['ligeti 'jorj 'Sa:ndor]; 28 May 1923 - 12 June 2006) was a Hungarian-Austrian composer of contemporary classical music. He has been described as "one of the most important avant-garde composers in the latter half of the twentieth century" and "one of the most innovative and influential among progressive figures of his time". Born in Transylvania, Romania, he lived in Hungary before emigrating to Austria in 1956, and became an Austrian citizen in 1968. In 1973 he became professor of composition at the Hamburg Hochschule fur Musik und Theater until he retired in 1989.

Ligeti was born in 1923 at Dicsoszentmarton (which was renamed Tarnaveni in 1941), in the Romanian region of Transylvania to Dr. Sandor Ligeti and Dr. Ilona Somogyi. His family was Hungarian Jewish. He was the grandnephew of the violinist Leopold Auer and cousin of Hungarian philosopher Agnes Heller.  Ligeti recalled that his first exposure to languages other than Hungarian came one day while listening to a conversation among the Romanian-speaking town police. Before that he had not known that other languages existed. He moved to Cluj with his family when he was six years old. He was not to return to the town of his birth until the 1990s. In 1940, Northern Transylvania was annexed by Hungary following the Second Vienna Award and Cluj became part of Hungary.  In 1941 Ligeti received his initial musical training at the conservatory in Cluj, and during the summers privately with Pal Kadosa in Budapest. In 1944, Ligeti's education was interrupted when he was sent to a forced labor brigade by the Horthy regime. His brother, age 16, was deported to the Mauthausen-Gusen concentration camp and both of his parents were sent to Auschwitz. His mother was the only other survivor of his immediate family.  Following World War II, Ligeti returned to his studies in Budapest, Hungary, graduating in 1949 from the Franz Liszt Academy of Music. He studied under Pal Kadosa, Ferenc Farkas, Zoltan Kodaly and Sandor Veress. He went on to do ethnomusicological research into the Hungarian folk music of Transylvania. However, after a year he returned to Franz Liszt Academy in Budapest, this time as a teacher of harmony, counterpoint and musical analysis, a position he secured with the help of Kodaly and held between 1950 and 1956. As a young teacher, Ligeti took the unusual step of regularly attending the lectures of an older colleague, the conductor and musicologist Lajos Bardos, a conservative Christian whose circle represented for Ligeti a safe haven, and whose help and advice he later acknowledged in the prefaces to his own two harmony textbooks (1954 and 1956). However, communications between Hungary and the West by then had become difficult due to the restrictions of the communist government, and Ligeti and other artists were effectively cut off from recent developments outside the Eastern Bloc.

What school he attended?
Following World War II, Ligeti returned to his studies in Budapest, Hungary, graduating in 1949 from the Franz Liszt Academy of Music.