I dig abstinence, and I think it should be taught -- to be sure.
I also believe that FAM should be taught to call boys and girls -- not so that they'll use it as a birth control method, but because knowledge (of bodies) often equates to power and the power to make better decisions.
I do wish I would have learned FAM a good decade before I did -- because I used it to solve many health problems, including those that impacted on fertility. We also used it as a method of birth control (i have not used chemical birth control -- i tried for one month, but just. . . didn't find it right for me), and then barrier methods and abstinence as well (particularly when fertile).
For me, I was raised understanding that sex had a lot of power -- and that it was a beautiful, wonderful thing that was both recreational and procreational. But it also has contexts, and requires responsibility.