SIOUX FALLS, S.D. (AP) — More than 100 students walked out of classes at a high school in Sioux Falls, South Dakota, calling attention to an epidemic of missing and murdered Indigenous women across the U.S.

The crowd of Washington High School students congregated Thursday morning at a nearby park to recognize thousands of missing and slain Indigenous women, the Sioux Falls Argus Leader reported.

“No one’s going to care if we go missing,” said Washington High School student Rosalia Szameit, who is Oglala Lakota, as tears welled in her eyes. “It’s unacceptable, and we have to do something.”

The Bureau of Indian Affairs’ Missing and Murdered Unit’s caseload covers a small fraction of an estimated 4,200 unsolved cases nationwide among American Indians and Alaska Natives, with the victims ranging in age from toddlers to the elderly. Indigenous people account for 3.5% of missing persons in the U.S. — more than three times the percentage in the overall population, according to federal data.

Despite some early success, most cases remain unsolved and federal officials have closed more than 300 potential cases due to jurisdictional conflicts — which prevent federal agents from working off-reservation without an invitation from local authorities — and other issues, The Associated Press reported in September.

U.S. officials have shared frustration over the unsolved cases, which critics say reflect racial injustice, particularly when compared to the response when a white woman goes missing.

The students who participated in the walkout “left school property to highlight their cause and did so respectfully and without disruption to others,” school district community relations coordinator DeeAnn Konrad said in a statement, the Argus Leader reported.

“Students, like all people, have constitutional rights to do as they wish as long as no laws are violated,” Konrad added. “Beyond those laws are school policy and attendance expectations. Skipping school for any reason is an unexcused absence.”