^I had my first period at 11 1/2 and it was the 20th century, switch.
when I had my period, I knew what to expect - it wasn't a shock. I had an elder sis (I think she got hers at 12) & she explained stuff to me. She also gave me a brochure that was given to her in school. During her time, some ppl from Johnson & Johnson went to the school and explained about menstruation, and gave free samples of sanitary pads. Well, eventually she used the pads but kept the brochure, which was good! During my time, the J&J ppl stopped giving freebies to schoolkids. I read the J&J brochure and learned a lot.
When I had my period, I wasn't the first one in my class who got it. Some already had it at age 11. Others had it later - 12 or 13. If you got it at 14, that was considered late already (among my school mates).