This survey explored how fifth-grade Mexican premenarcheal girls (N = 80) and their teachers (N = 16) view the preparation students receive about menstruation at school. The most discussed topics in class included hygiene and body functions. The main discrepancies between girls and teachers were as follows: (a) more teachers than girls reported that they discussed the emotional aspects of menses. (b) teachers indicated that their pupils were better prepared than the students themselves believed, (c) more teachers reported that the girls acted ashamed during the classes, and (d) more girls perceived that boys behaved in a mocking manner, whereas more teachers thought that the boys acted nervous. In conclusion, teaching about menstruation is problematic, but these findings provide information for teachers to meet the needs of girls more efficiently.