Actually…they say you can but don’t recommend it because if it fails…the chances you’ll get pregnant is significantly higher then typical condom use.
That’s what I read in FAM-based Taking Charge of Your Fertility.
They said if you are really serious about avoiding then abstinence is best and recommended.
Well, that makes a lot more sense, than my understanding of FAM as “the same as NFP, except that the couple can use condoms when fertile”. I kept thinking “So, the idea is for couples to undertake all that laborious work of checking and charting, just so they can find out when they get to have sex without condoms? Is sex with condoms really THAT horrible?”
Anyway, to get back to the actual question. I think that it is very important for a woman to be familiar with her own menstrual cycle and how her own body works (or doesn’t work), whether she’s Catholic or not.
I do track my own cycles using a “period pal” app and while I don’t use it for family planning, as I realize that NFP is more sophisticated than just a calendar rhythm method, it is very helpful in tracking certain symptoms that pop up, or just predicting periods at all – I was taught a very simple “a woman gets a period once a month” version of the cycle as a teenager, and I literally expected it to start on the same day of every month and got very anxious and assumed I had “irregular cycles” because it didn’t. As it turns out my cycles are usually VERY regular.
As for “will teaching NFP make kids more likely to have sex” – same debate for ABC, the HPV vaccine (and before it was made an infant vaccine, the hepatitis B vaccine), etc. Yes, I was a teenager when the Hepatitis B vaccine was introduced. I remember a very similar debate about whether giving teens Hepatitis B vaccine would make it more likely for them to have sex or use drugs, as those are the primary modes of transmission in the US. Since the vaccine was later incorporated into the baby vaccine schedule, that debate got cut off before there was any real evidence about it one way or the other.
BTW my own mother, while very conservative about sex, had no problem with me getting the vaccine. I later realized one reason is because she unfortunately knew some girls who got pregnant from nonconsensual, or at least very exploitative sex (20 year old men having sex with 14 year old girls) and realized that kids can be at risk of STDs even if they themselves are chaste. This kind of exploitation almost happened to my own sister.

Unfortunately sexual violence is not uncommon and I think that’s another factor to consider in these discussions.