“Pine Ridge Indian Reservation, S.D. ― Dominique Amiotte, 17, always makes sure to keep a few extra tampons in her locker. It’s not much, but it’s enough to encourage at least some of her struggling friends to come to school when they have their periods.

About half of Amiotte’s girlfriends can’t afford tampons or sanitary pads. As a result, when they menstruate, they’ll skip school for as long as a week. This can lead them to fall behind in class, contributing to the already abysmal graduation rates on the Pine Ridge Indian Reservation. There are no official records on how many of the young women at the reservation’s 13 schools have felt the consequences of this issue, but individuals we spoke to say it’s an inescapable part of everyday life.

“It makes me angry,” Amiotte told HuffPost unflinchingly while seated in an empty classroom at the Crazy Horse School, where there are 70 girls enrolled in middle or high school classes.”