(Materal by Rabbi Kenneth Auman, presented by Chana. All mistakes are my fault.)
This is from the Likutei Halachos written by the Chafetz Chaim. There are certain masechtos where the Rif didn't write his commentary because it's not nogea l'halacha. So the Chafetz Chaim made a compendium of these areas that the Rif left out. So he has a commentary here.
Please look at the following two pages:
So this quotes the gemara from Sotah about teaching daughters, and how teaching them Torah is equivalent to teaching them tiflus.
What's of interest is next to the words "af she'ain l'lamda" there are three asterisks. Go down and see what the Chafetz Chaim says in the footnote. He says that this (that teaching one's daughter Torah is like teaching her tiflus) refers to those times where daughters breathed the air of Judaism, grew up with role models and examples, and practiced what her father did. But in our generation, which is much weaker, where our daughters are learning the foreign language of the country where they live- if you don't teach your daughters Torah, then they will God forbid not be well-versed or knowledgeable in understanding their religion. Because daughters are going to the Gymnasium (secular school) and people have moved and spread out you need to teach women the written Torah.
(So we have a question on this- how can the Chafetz Chaim possibly do this? This is apparently a halakha, and he seems to simply be stating that the times have changed, so what we're doing has changed. How can he say this?)
The simple interpretation of the Chafetz Chaim is that he's simply expanding the parameters of the Ramah's idea, and making more relevant to women (and since more is relevant, women can learn more. It's already accepted that women can learn what is relevant to them.)