CS, ir miklat is till the Kohein Gadol is niftar, not for life.
The prohibition against teaching Torah shebalpeh (i.e Gemorah, etc.) to girls/women is a Halacha in the Gemorah that the Shulchan Aruch and Rema (and everyone since Chazal through the times of the Chofetz Chaim) pasken l’Halacha. The Chofetz Chaim issued a heter due to the shas hadchak to teach girls Torah formally in schools, something that until that time had virtually never occurred in Klal due to the aforementioned Halacha.