Rabbi Moshe Feinstein and others argue that the “great reform” [Hebrew, tiqqun] made on the intermediate festival day ritual of water drawing in the Temple is the “source” for the synagogue partition. A formal separation was made in the Temple based on an obscure verse preserved by the Chronicler. There are three difficulties with this reading.
One does not derive Torah law from a Biblical book that is post-Torah, and the Chronicles were among the last books of Hebrew Scripture to have been written, by all accounts. Second, the idiom tiqqun, enactment, is a human made law that by definition cannot be a Scriptural obligation. This problem was also noted by the ultra Orthodox Haredi Rabbi Yom Tov Scwhartz, who answered [Me’aneh] the letters, Iggrot, or responsa, of R.Feinstein. Third, we do not have basins, sacrifices, or necessarily raised women sections in the synagogue. And men were allowed in the women’s section on occasion, as noted above.
Feinstein was scandalized with mixed gender seating at the time of prayer, and he claimed that this mixing and contact, even if unintentional, violates the principle prohibiting levity or qallut rosh. According to the Talmud, one may not practice qallut roshin a synagogue, indicating that the entire category is conventional and not covenantal. I do not recall that qallut rosh ever refers to a Pentateuchal law. Oddly, R. Feinstein is unwavering regarding the synagogue mechitsa, which is not mentioned in the oral Torah canon, but deems it satisfactory to allow eating in batei midrash, or small chapels of Hassidic prayer, treating them with the leniency of a study academy. While the Talmud does not mention mixed gender settings pre se to be qallut rosh, eating is the synagogue most assuredely is qallut rosh. R. Feinstein’s vehemence has carried the day in Orthodox culture, and the mechitsa has become a defining institution within Orthodoxy.
Rabbi Alan Yuter, “The Low Down on the Height of the Mechitsa: A Modern Orthodox Reading”, UTJ Viewpoints (6 July 2007) [http://viewpoints.utj.org/?p=63]