“A Lethal Education” explores the lethal consequences of United States educational policies that removed Native American children and young adults from their homes, placed them in institutions designed to destroy Indigenous languages, cultures, and traditions, and supplanted them with non-Indigenous substitutes. In particular, this dissertation explores the loss of life associated with United States boarding schools for American Indians and Alaska Natives. It examines how and why off-reservation boarding schools promoted contagion and incubated infections with lethal consequences for many Native American students. Admitting ill students, substandard housing, overcrowding, forced labor, physical, mental, and sexual abuse, malnourishment, dietary insufficiencies, psychological trauma, and willful neglect compromised student immune systems leaving them vulnerable to pathogens. These factors also impaired immunological defenses, decreasing the chances of recovery once a student became infected. Diseases, including diphtheria, influenza, measles, mumps, smallpox, and trachoma, spread and epidemics swept through student populations. At the Carlisle Indian Industrial School in Pennsylvania, Forest Grove Indian Training School in Oregon, Chemawa Indian School in Oregon, Haskell Institute in Kansas, Perris Indian School in California, and Sherman Institute in California, recurring infectious disease outbreaks then led to elevated tuberculosis rates. Such outbreaks and infections killed hundreds of Indigenous students at these schools, leaving death, shattered families, and devastated communities in their wake. Based upon newly opened archives, this study deploys a historical epidemiological approach relatively new to Native American boarding school studies. Ultimately, the findings reveal that thousands of American Indian and Alaska Native students perished at off-reservation Native American boarding schools, while officials sent thousands more home to die. These deaths were the result of dangerous local school policies, parsimonious congressional funding, and gross negligence by federal officials in the United States Office of Indian Affairs.