Education also prevents teen pregnancies, primarily by giving women other ways to spend their time and define their self-worth than babby, and also making it so that they don't have to effectively get work as a wife & mother. It's one of those feedback loops that builds and builds.
Let me put it this way. Ya want yer girl's first job to not be being a Mom? You gotta train her with skills for other jobs, because I can guarantee you that from the age of 9 or so, if not sooner, a bunch of older women have been teaching her how to be a mom.
Help her get work as something other than a babysitter. Make sure she gets paid for that work. Make sure that if she dates a guy, not only does she have access to contraception and whatnot, but she also has a sense of her own value outside of her attachment to him and her ability to provide children.
And if she does get pregnant, make sure that there is a route back into education, so that, again, she doesn't just get stuck on team babby-babby-babby.
As a note I have known women who said that they wished, instead of being sent to college, they had been told about the joys of being a wife and mother and just gotten married at age 18. To be fair this woman I am thinking of is an age thirties-ish queer evangelical Christian. But they do exist.
The point is not to force women to become scientists if they don't want. The point is to make sure that there is always something for them to do, which brings them a sense of value, besides producing with their bodies.
Finally: If the Taliban are saying, "We will allow women to be educated up til age 18," that is a different thing from "we will allow their education up to menarche," which is again a different thing from "we will allow their education provided that they are not married." It could mean so many things. But perhaps something to notice is that all of these are what is called a "negative reward" in psychology. "We will not prevent women and girls to be educated up until such and such an event" is different from "we affirm the right of women and girls to pursue education and will facilitate it as much as possible under our regime."
I'm not interested in arguing about it, primarily because our own education system is so fucked that although I very sincerely hope that Afghanistan becomes a good, pleasant place to live and people stop bombing the shit out of it, I also know that those in glass houses should not throw stones, even if the other dude's house is all-glass as opposed to your own half-glass domain.