R. Jeffrey Saks suggested that I post the following letter from R. Joseph B. Soloveitchik, Community, Covenant, and Commitment: Selected Letters and Communications, p. 83:
Rabbi Leonard Rosenfeld
c/o Rabbi Leo Jung
210 West 90th Street
New York 24, N.Y.
May 27, 1953Dear Rabbi Rosenfeld:
Please accept my apologies for not answering your letters sooner. The delay was due to my overcrowded schedule. As to your question with regard to a curriculum in a coeducational school, I expressed my opinion to you long ago that it would be a very regrettable oversight on our part if we were to arrange separate Hebrew courses for girls. Not only is the teaching of Torah she-be-al peh to girls permissible but it is nowadays an absolute imperative. This policy of discrimination between the sexes as to subject matter and method of instruction which is still advocated by certain groups within our Orthodox community has contributed greatly to the deterioration and downfall of traditional Judaism. Boys and girls alike should be introduced into the inner halls of Torah she-be-al peh.
I hope to prepare in the near future a halakhic brief on the problem which will exhaust the various aspects of the same. In the meantime I heartily endorse a uniform program for the entire student body.
With kindest personal regards, I remain