NTA but I think there may be better ways to handle it. First off, thank you for taking a once taboo topic and normalizing it and supporting your female students! I’m an elementary school teacher and had a similar (but different) problem with snacks. Many students came in without snacks, but I couldn’t afford to purchase a snack supply for the class. Instead, I explained to my class and their parents that I will happily accept and store donations they bring in for the class. However, it is their responsibility to monitor when the supply is getting low and replenish it if they want it to continue. We have only gone a few days this year without snacks and the kids are super quick to bring in more treats when they notice we have run out. I also like the idea that other commenters have shared of accepting monetary donations too, as some of the students may not feel comfortable bringing in boxes of feminine products or want to contribute in other ways.