Synagogue, the Great means in the bible: It is believed to have consisted of a series of Jewish teachers, 430-300 B.C.. Nehemiah, the founder of the group, Simon the Just the final member, with 120 total. According to the Talmud, this group is responsible for compiling the Old Testament canon and establishing schools for teaching the law. These traditions are not supported by historical evidence, so it’s doubtful that there was ever a Great Synagogue.
(in Bible Dictionary)