Your girl getting her First period can be a very overwhelming experience for a mom. Generally, now as days schools do take sessions in class 5/6 for girl students on menstruation, though I strongly feel that such sessions are equally important for the boys.
As mom we talk to our girls about periods generally around the age of 8-9 years. Various factors like pollution, food quality and generally stress level have strong connection with first menstruation in girls. Though moms talk to the little one about this natural process, almost all the moms always feel/want that their daughter must get her First Periods